Wireless communications over unlicensed radio frequency spectrum

ABSTRACT

Techniques for transmitting and receiving wireless communications over an unlicensed radio frequency spectrum band are disclosed, including techniques for transmitting and receiving system information blocks over the unlicensed radio frequency spectrum band, techniques for gaining access to the unlicensed radio frequency spectrum band by performing extended clear channel assessments (ECCAs), techniques for transmitting and receiving synchronization signals and reference signals over the unlicensed radio frequency spectrum band, techniques for identifying starting times of downlink transmissions over the unlicensed radio frequency spectrum band, techniques for transmitting and receiving clear channel assessment (CCA)-exempt transmissions over the unlicensed radio frequency spectrum band, techniques for performing random access over the unlicensed radio frequency spectrum band, and techniques for dynamically modifying a transmission mode over the unlicensed radio frequency spectrum band.

CROSS REFERENCES

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 15/956,551 by Malladi et al., entitled “WirelessCommunications Over Unlicensed Radio Frequency Spectrum” filed Apr. 18,2018, which is a continuation of U.S. patent application Ser. No.14/736,867 by Malladi, et al., entitled “Wireless Communications OverUnlicensed Radio Frequency Spectrum” filed Jun. 11, 2015, which claimspriority to U.S. Provisional Patent Application No. 62/012,231 byMalladi et al., entitled “Wireless Communications Over Unlicensed RadioFrequency Spectrum,” filed Jun. 13, 2014; each of which is assigned tothe assignee hereof and expressly incorporated by reference herein.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to wireless communicationsystems, and more particularly to wireless communications using, atleast in part, unlicensed radio frequency spectrum band.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing the available system resources (e.g., time, frequency, andpower). Examples of such multiple-access systems include code-divisionmultiple access (CDMA) systems, time-division multiple access (TDMA)systems, frequency-division multiple access (FDMA) systems, andorthogonal frequency-division multiple access (OFDMA) systems.

By way of example, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple user equipments (UEs). A base station maycommunicate with UEs on downlink channels (e.g., for transmissions fromthe base station to the UE) and uplink channels (e.g., for transmissionsfrom the UEs to the base station).

Some modes of communication may enable communications with a UE overdifferent radio frequency spectrum bands (e.g., a licensed radiofrequency spectrum band and/or an unlicensed radio frequency spectrumband) of a cellular network. With increasing data traffic in cellularnetworks that use licensed radio frequency spectrum bands, offloading atleast some data traffic to an unlicensed radio frequency spectrum bandmay provide a cellular operator with opportunities for enhanced datatransmission capacity. Prior to gaining access to, and communicatingover, the unlicensed radio frequency spectrum band, a device, mayperform a listen before talk (LBT) procedure to contend for access tothe unlicensed radio frequency spectrum band. An LBT procedure mayinclude performing a clear channel assessment (CCA) to determine whethera channel of the unlicensed radio frequency spectrum band is available.If it is determined that the channel of the unlicensed radio frequencyspectrum band is not available (e.g., because another device is alreadyusing the channel of the unlicensed radio frequency spectrum band), aCCA may be performed for the channel again at a later time. If thechannel is available, the device may begin to transmit data using thechannel.

SUMMARY

The present disclosure, for example, relates to wireless communicationsover an unlicensed radio frequency spectrum band, including techniquesfor transmitting and receiving system information blocks over theunlicensed radio frequency spectrum band, techniques for gaining accessto the unlicensed radio frequency spectrum band by performing extendedclear channel assessments (ECCAs), techniques for transmitting andreceiving synchronization signals and reference signals over theunlicensed radio frequency spectrum band, techniques for identifyingstarting times of downlink transmissions over the unlicensed radiofrequency spectrum band, techniques for transmitting and receiving clearchannel assessment (CCA)-exempt transmissions over the unlicensed radiofrequency spectrum band, techniques for performing random access overthe unlicensed radio frequency spectrum band, and techniques fordynamically modifying a transmission mode over the unlicensed radiofrequency spectrum band.

A method for wireless communication is described, the method comprisinggenerating a system information block comprising a plurality ofparameters related to a base station, wherein the parameters comprise atleast one listen before talk (LBT) parameter, at least one cellidentifier, and at least one radio frame identifier, and transmittingthe system information block over an unlicensed radio frequency spectrumband.

An apparatus for wireless communication is described, the apparatuscomprising means for generating a system information block comprising aplurality of parameters related to a base station, wherein theparameters comprise at least one LBT parameter, at least one cellidentifier, and at least one radio frame identifier, and means fortransmitting the system information block over an unlicensed radiofrequency spectrum band.

An apparatus for wireless communication is described, the apparatuscomprising a processor and memory coupled with the processor, whereinthe processor is configured to generate a system information blockcomprising a plurality of parameters related to a base station, whereinthe parameters comprise at least one LBT parameter, at least one cellidentifier, and at least one radio frame identifier, and transmit thesystem information block over an unlicensed radio frequency spectrumband.

A non-transitory computer-readable medium storing instructions forwireless communication is also described, the instructions comprisinginstructions executable by a processor to generate a system informationblock comprising a plurality of parameters related to a base station,wherein the parameters comprise at least one LBT parameter, at least onecell identifier, and at least one radio frame identifier, and transmitthe system information block over an unlicensed radio frequency spectrumband.

According to some aspects of the method, apparatuses, and/ornon-transitory computer-readable medium, the system information block istransmitted over the unlicensed radio frequency spectrum band during aclear channel assessment (CCA)-exempt transmission (CET) subframeassociated with the base station. In some examples the CET subframe isperiodic and transmitting the system information block comprisestransmitting the system information block at each instance of the CET.

According to some aspects of the method, apparatuses, and/ornon-transitory computer-readable medium, a CCA may be performed prior toa non-CET subframe associated with opportunistic system informationblock transmissions, and the system information block may be transmittedon the non-CET subframe when the CCA is successful. Different redundancyversions of the system information block may be transmitted at differenttime intervals.

Some aspects of the method, apparatuses, and/or non-transitorycomputer-readable medium may further comprise dynamically modifying theLBT parameter, and transmitting an updated version of the systeminformation block at a next CET subframe. In some examples the at leastone cell identifier is selected from the group consisting of a physicalcell identifier (PID), an operator identifier, a cell global identity(CGI), and combinations thereof.

In some aspects of the method, apparatuses, and/or non-transitorycomputer-readable medium, the at least one LBT parameter is selectedfrom the group consisting of an extended clear channel assessment (ECCA)counter parameter, a CCA energy threshold, a guard period for basestation resynchronization, and combinations thereof. In some examples anECCA procedure at the base station is identical for unicast andbroadcast transmissions.

In some aspects of the method, apparatuses, and/or non-transitorycomputer-readable medium, the radio frame identifier comprises a systemframe number (SFN). In some examples the system information block spansan entire bandwidth of a component carrier associated with theunlicensed radio frequency spectrum band.

The foregoing has outlined features and technical advantages of examplesaccording to the disclosure to clarify the detailed description.Additional features and advantages will be described hereinafter. Theconception and specific examples disclosed may be readily utilized as abasis for modifying or designing other structures for carrying out thesame purposes of the present disclosure. Such equivalent constructionsdo not depart from the scope of the appended claims. Characteristics ofthe concepts disclosed herein, both their organization and method ofoperation, together with associated advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. Each of the figures is provided for the purpose ofillustration and description only, and not as a definition of the limitsof the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows an example of a wireless communication system, inaccordance with various aspects of the present disclosure;

FIG. 2 shows a wireless communication system in which LTE/LTE-A isdeployed under different scenarios using an unlicensed radio frequencyspectrum band, in accordance with various aspects of the presentdisclosure;

FIG. 3 shows seven TDD configurations that may be used for LTE/LTE-Acommunications in an LBT radio frame transmitted over an unlicensedradio frequency spectrum band, in accordance with various aspects of thepresent disclosure;

FIG. 4 shows a block diagram of a base station for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 5 shows a block diagram of a base station for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 6 shows a block diagram of a UE that may be used in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 7 shows a block diagram of a UE that may be used for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 8 shows a timing diagram illustrating the transmission of aplurality of parameters during a CET subframe over an unlicensed radiofrequency spectrum band, in accordance with various aspects of thepresent disclosure;

FIG. 9 shows a diagram of a radio frame defining a plurality ofsubframes for a particular TDD configuration, in accordance with variousaspects of the present disclosure;

FIG. 10 shows a diagram of a radio frame illustrating an ECCA subframe,in accordance with various aspects of the present disclosure;

FIG. 11 shows a diagram of a radio frame illustrating a location infrequency and time of one or more synchronization signals (e.g., ePSS,eSSS, or a combination thereof) and an eCRS signal, in accordance withvarious aspects of the present disclosure;

FIG. 12 shows a diagram of a radio frame illustrating a transmission ofa D-CUBS during the radio frame, in accordance with various aspects ofthe present disclosure;

FIG. 13 shows a diagram illustrating another timing diagram of certainsubframes, in accordance with various aspects of the present disclosure;

FIG. 14 shows a diagram illustrating an uplink CET (U-CET) subframe, inaccordance with various aspects of the present disclosure;

FIG. 15 shows a diagram illustrating an enlarged interlace of the U-CET,in accordance with various aspects of the present disclosure;

FIG. 16 shows a diagram corresponding to random access channels inaccordance with various aspects of the present disclosure;

FIG. 17 shows a diagram of a radio subframe and an ECCA subframe for usein an ECCA procedure for uplink transmissions, in accordance withvarious aspects of the present disclosure;

FIG. 18 shows a diagram of an enlarged interlace for use in an uplinkSC-FDMA transmission, in accordance with various aspects of the presentdisclosure;

FIG. 19 shows a diagram of an enlarged interlace for use in an uplinkOFDMA transmission, in accordance with various aspects of the presentdisclosure;

FIGS. 20-38 show flowcharts illustrating methods for wirelesscommunication in accordance with various aspects of the presentdisclosure;

FIG. 39 shows a diagram of a system for use in wireless communicationsin accordance with various aspects of the present disclosure; and

FIG. 40 shows a diagram of a system for use in wireless communicationsin accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Techniques are described in which unlicensed radio frequency spectrumband is used for at least a portion of a wireless communications system.In some examples, the unlicensed radio frequency spectrum band may beused for Long Term Evolution (LTE) communications and/or LTE-Advanced(LTE-A) communications. The unlicensed radio frequency spectrum band maybe used in combination with, or independent from, a licensed radiofrequency band. In some examples, the unlicensed radio frequencyspectrum band may be a radio frequency spectrum band for which a devicemay need to contend for access because the radio frequency spectrum bandis available, at least in part, for unlicensed use (e.g., Wi-Fi useand/or LTE/LTE-A use in an unlicensed radio frequency spectrum band).

With increasing data traffic in cellular networks that use a licensedradio frequency spectrum band, offloading of at least some data trafficto an unlicensed radio frequency spectrum band may provide a cellularoperator (e.g., an operator of a public land mobile network (PLMN)and/or a coordinated set of base stations defining a cellular network,such as an LTE/LTE-A network) with opportunities for enhanced datatransmission capacity. As noted above, before communicating over theunlicensed radio frequency spectrum band, devices may perform a listenbefore talk (LBT) procedure to gain access to the unlicensed radiofrequency spectrum band. Such an LBT procedure may include performing aclear channel assessment (CCA) to determine whether a channel of theunlicensed radio frequency spectrum band is available.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in other examples.

FIG. 1 shows an example of a wireless communication system 100, inaccordance with various aspects of the present disclosure. The wirelesscommunication system 100 may include base stations 105 (e.g., basestations forming parts or all of one or more eNBs), a number of userequipments (UEs) 115, and a core network 130. Some of the base stations105 may communicate with the UEs 115 under the control of a base stationcontroller (not shown), which may be part of the core network 130 orcertain ones of the base stations 105 in various examples. Some of thebase stations 105 may communicate control information and/or user datawith the core network 130 through backhaul 132. In some examples, someof the base stations 105 may communicate, either directly or indirectly,with each other over backhaul links 134, which may be wired or wirelesscommunication links. The wireless communication system 100 may supportoperation on multiple carriers (waveform signals of differentfrequencies). Multi-carrier transmitters can transmit modulated signalssimultaneously on the multiple carriers. For example, each communicationlink 125 may be a multi-carrier signal modulated according to variousradio technologies. Each modulated signal may be sent on a differentcarrier and may carry control information (e.g., reference signals,control channels, etc.), overhead information, data, etc.

The base stations 105 may wirelessly communicate with the UEs 115 viaone or more base station antennas. Each of the base stations 105 mayprovide communication coverage for a respective coverage area 110. Insome examples, a base station 105 may be referred to as an access point,a base transceiver station (BTS), a radio base station, a radiotransceiver, a basic service set (BSS), an extended service set (ESS), aNodeB, an evolved NodeB (eNB), a Home NodeB, a Home eNodeB, a wirelesslocal area network (WLAN) access point, a Wi-Fi node or some othersuitable terminology. The coverage area 110 for a base station 105 maybe divided into sectors making up only a portion of the coverage area.The wireless communication system 100 may include base stations 105 ofdifferent types (e.g., macro, micro, and/or pico base stations). Thebase stations 105 may also utilize different radio technologies, such ascellular and/or WLAN radio access technologies. The base stations 105may be associated with the same or different access networks or operatordeployments (e.g., collectively referred to herein as “operators”). Thecoverage areas of different base stations 105, including the coverageareas of the same or different types of base stations 105, utilizing thesame or different radio technologies, and/or belonging to the same ordifferent access networks, may overlap.

In some examples, the wireless communication system 100 may include anLTE/LTE-A communication system (or network), which may support one ormore modes of operation or deployment in a first radio frequencyspectrum band (e.g., a radio frequency spectrum band for which devicesdo not contend for access because the radio frequency spectrum band islicensed to particular users for particular uses, such as a licensedradio frequency spectrum band usable for LTE/LTE-A communications)and/or a second radio frequency spectrum band (e.g., an unlicensed radiofrequency spectrum band such as an unlicensed radio frequency spectrumband for which devices may need to contend for access because the radiofrequency spectrum band is available for unlicensed use, such as Wi-Fiuse, or a licensed radio frequency spectrum band for which devices mayneed to contend for access because the radio frequency spectrum band isavailable for use by two or more operators on a contention basis). Inother examples, the wireless communication system 100 may supportwireless communication using one or more access technologies differentfrom LTE/LTE-A. In LTE/LTE-A communication systems, the term evolvedNodeB or eNB may be, for example, used to describe ones or groups of thebase stations 105.

The wireless communication system 100 may be or include an LTE/LTE-Anetwork in which different types of base stations 105 provide coveragefor various geographical regions. For example, each base station 105 mayprovide communication coverage for a macro cell, a pico cell, a femtocell, and/or other type of cell. Small cells such as pico cells, femtocells, and/or other types of cells may include low power nodes (LPNs). Amacro cell, for example, covers a relatively large geographic area(e.g., several kilometers in radius) and may allow unrestricted accessby UEs with service subscriptions with the network provider. A pico cellwould, for example, cover a relatively smaller geographic area and mayallow unrestricted access by UEs with service subscriptions with thenetwork provider. A femto cell would also, for example, cover arelatively small geographic area (e.g., a home) and, in addition tounrestricted access, may also provide restricted access by UEs having anassociation with the femto cell (e.g., UEs in a closed subscriber group(CSG), UEs for users in the home, and the like). An eNB for a macro cellmay be referred to as a macro eNB. An eNB for a pico cell may bereferred to as a pico eNB. And, an eNB for a femto cell may be referredto as a femto eNB or a home eNB. An eNB may support one or multiple(e.g., two, three, four, and the like) cells.

The core network 130 may communicate with the base stations 105 via abackhaul 132 (e.g., S1 application protocol, etc.). The base stations105 may also communicate with one another, e.g., directly or indirectlyvia backhaul links 134 (e.g., X2 application protocol, etc.) and/or viabackhaul 132 (e.g., through core network 130). The wirelesscommunication system 100 may support synchronous or asynchronousoperation. For synchronous operation, the eNBs may have similar frameand/or gating timing, and transmissions from different eNBs may beapproximately aligned in time. For asynchronous operation, the eNBs mayhave different frame and/or gating timing, and transmissions fromdifferent eNBs may not be aligned in time.

The UEs 115 may be dispersed throughout the wireless communicationsystem 100. A UE 115 may also be referred to by those skilled in the artas a mobile device, a mobile station, a subscriber station, a mobileunit, a subscriber unit, a wireless unit, a remote unit, a wirelessdevice, a wireless communication device, a remote device, a mobilesubscriber station, an access terminal, a mobile terminal, a wirelessterminal, a remote terminal, a handset, a user agent, a mobile client, aclient, or some other suitable terminology. A UE 115 may be a cellularphone, a smartphone, a personal digital assistant (PDA), a wirelessmodem, a wireless communication device, a handheld device, a tabletcomputer, a laptop computer, a cordless phone, a wearable item such as awatch or glasses, a wireless local loop (WLL) station, etc. A UE 115 maybe able to communicate with macro eNBs, pico eNBs, femto eNBs, relays,and the like. A UE 115 may also be able to communicate over differenttypes of access networks, such as cellular or other wireless wide areanetwork (WWAN) access networks, or WLAN access networks. In some modesof communication with a UE 115, communication may be conducted over aplurality of communication links 125 or channels (i.e., componentcarriers), with each channel using a component carrier between the UE115 and one of a number of cells (e.g., serving cells, which cells mayin some cases be operated by the same or different base stations 105).

Each component carrier may be provided over the first (e.g., licensed)radio frequency spectrum band or the second (e.g., unlicensed) radiofrequency spectrum band, and a set of component carriers used in aparticular mode of communication may all be received (e.g., at a UE 115)over the first radio frequency spectrum band, all be received over thesecond radio frequency spectrum band, or be received over a combinationof the first radio frequency spectrum band and the second radiofrequency spectrum band.

The communication links 125 shown in wireless communication system 100may include uplink channels (using component carriers) for carryinguplink (UL) communications (e.g., transmissions from a UE 115 to a basestation 105) and/or downlink channels (using component carriers) forcarrying downlink (DL) communications (e.g., transmissions from a basestation 105 to a UE 115). The UL communications or transmissions mayalso be called reverse link communications or transmissions, while theDL communications or transmissions may also be called forward linkcommunications or transmissions. The downlink communications and/oruplink communications may be made using the first (e.g., licensed) radiofrequency spectrum band, the second (e.g., unlicensed) radio frequencyspectrum band, or both.

In some examples of the wireless communication system 100, LTE/LTE-A maybe deployed under different scenarios using the second (e.g.,unlicensed) radio frequency spectrum band. The deployment scenarios mayinclude a supplemental downlink mode in which LTE/LTE-A downlinkcommunications in the first (e.g., licensed) radio frequency spectrumband may be offloaded to the second radio frequency spectrum band, acarrier aggregation mode in which both LTE/LTE-A downlink and uplinkcommunications may be offloaded from the first radio frequency spectrumband to the second radio frequency spectrum band, and/or a standalonemode in which LTE/LTE-A downlink and uplink communications between abase station 105 and a UE 115 may solely occur using the second radiofrequency spectrum band. Base stations 105 as well as UEs 115 may insome examples support one or more of these or similar modes ofoperation. Orthogonal frequency division multiple access (OFDMA)waveforms may be used in the communication links 125 for LTE/LTE-Adownlink communications in the first (e.g., licensed) radio frequencyspectrum band and/or the second (e.g., unlicensed) radio frequencyspectrum band, while OFDMA, single-carrier frequency division multipleaccess (SC-FDMA) and/or resource block interleaved FDMA waveforms may beused in the communication links 125 for LTE/LTE-A uplink communicationsin the first radio frequency spectrum band and/or the second (e.g.,unlicensed) radio frequency spectrum band.

FIG. 2 shows a wireless communication system 200 in which LTE/LTE-A isdeployed under different scenarios using an unlicensed radio frequencyspectrum band, in accordance with various aspects of the presentdisclosure. More specifically, FIG. 2 illustrates examples of asupplemental downlink mode, a carrier aggregation mode, and a standalonemode in which LTE/LTE-A is deployed using an unlicensed radio frequencyspectrum band. The wireless communication system 200 may be an exampleof portions of the wireless communication system 100 described withreference to FIG. 1. Moreover, a first base station 105-a-1 and a secondbase station 105-a-2 may be examples of aspects of one or more of thebase stations 105 described with reference to FIG. 1, while a first UE115-a-1, a second UE 115-a-2, a third UE 115-a-3, and a fourth UE115-a-4 may be examples of aspects of one or more of the UEs 115described with reference to FIG. 1.

In the example of a supplemental downlink mode in the wirelesscommunication system 200, the first base station 105-a-1 may transmitOFDMA waveforms to the first UE 115-a-1 using a downlink channel 220.The downlink channel 220 may be associated with a frequency F1 in anunlicensed radio frequency spectrum band. The first base station 105-a-1may also transmit OFDMA waveforms to the first UE 115-a-1 using a firstbidirectional link 225 and may receive SC-FDMA waveforms from the firstUE 115-a-1 using the first bidirectional link 225. The firstbidirectional link 225 may be associated with a frequency F4 in alicensed radio frequency spectrum band. The downlink channel 220 in theunlicensed radio frequency spectrum band and the first bidirectionallink 225 in the licensed radio frequency spectrum band may operateconcurrently. The downlink channel 220 may provide a downlink capacityoffload for the first base station 105-a-1. In some examples, thedownlink channel 220 may be used for unicast services (e.g., addressedto one UE) or for multicast services (e.g., addressed to several UEs).This supplemental downlink mode may be employed by a service provider(e.g., a mobile network operator (MNO)) using a licensed radio frequencyspectrum where additional downlink bandwidth is needed.

In one example of a carrier aggregation mode in the wirelesscommunication system 200, the first base station 105-a-1 may transmitOFDMA waveforms to the second UE 115-a-2 using a second bidirectionallink 230 and may receive OFDMA waveforms, SC-FDMA waveforms, and/orresource block interleaved FDMA waveforms from the second UE 115-a-2using the second bidirectional link 230. The second bidirectional link230 may be associated with the frequency F1 in the unlicensed radiofrequency spectrum band. The first base station 105-a-1 may alsotransmit OFDMA waveforms to the second UE 115-a-2 using a thirdbidirectional link 235 and may receive SC-FDMA waveforms from the secondUE 115-a-2 using the third bidirectional link 235. The thirdbidirectional link 235 may be associated with a frequency F2 in alicensed radio frequency spectrum band. The second bidirectional link230 may provide a downlink and uplink offloading for the thirdbidirectional link 235. This carrier aggregation mode may be employed bya service provider using a licensed radio frequency spectrum whereadditional downlink bandwidth and additional uplink bandwidth areneeded.

In another example of a carrier aggregation mode in the wirelesscommunication system 200, the first base station 105-a-1 may transmitOFDMA waveforms to the third UE 115-a-3 using a fourth bidirectionallink 240 and may receive OFDMA waveforms, SC-FDMA waveforms, and/orresource block interleaved waveforms from the third UE 115-a-3 using thefourth bidirectional link 240. The fourth bidirectional link 240 may beassociated with a frequency F3 in the unlicensed radio frequencyspectrum band. The first base station 105-a-1 may also transmit OFDMAwaveforms to the third UE 115-a-3 using a fifth bidirectional link 245and may receive SC-FDMA waveforms from the third UE 115-a-3 using thefifth bidirectional link 245. The fifth bidirectional link 245 may beassociated with the frequency F2 in the licensed radio frequencyspectrum band. The fourth bidirectional link 240 may provide a downlinkand uplink capacity offload for the first base station 105-a-1. Thisexample and those provided above are presented for illustrative purposesand there may be other similar modes of operation or deploymentscenarios that combine LTE/LTE-A in licensed radio frequency spectrumband and unlicensed radio frequency spectrum band for capacity offload.

As described above, one type of service provider that may benefit fromthe capacity offload offered by using LTE/LTE-A in unlicensed radiofrequency spectrum band is a traditional MNO having access rights to anLTE/LTE-A licensed radio frequency spectrum band. For these serviceproviders, an operational example may include a bootstrapped mode (e.g.,supplemental downlink, carrier aggregation) that uses the LTE/LTE-Aprimary component carrier (PCC) on the licensed radio frequency spectrumband and at least one secondary component carrier (SCC) on theunlicensed radio frequency spectrum band.

In the carrier aggregation mode, data and control may, for example, becommunicated in the licensed radio frequency spectrum (e.g., via firstbidirectional link 225, third bidirectional link 235, and fifthbidirectional link 245) while data may, for example, be communicated inthe unlicensed radio frequency spectrum band (e.g., via secondbidirectional link 230 and fourth bidirectional link 240). The carrieraggregation mechanisms supported when using unlicensed radio frequencyspectrum band may fall under a hybrid frequency division duplex-timedivision duplex (FDD-TDD) carrier aggregation or a TDD-TDD carrieraggregation with different symmetry across component carriers.

Still referring to FIG. 2, in an example of a standalone mode in thewireless communication system 200, the second base station 105-a-2 maytransmit OFDMA waveforms to the fourth UE 115-a-4 using a bidirectionallink 250 and may receive OFDMA waveforms, SC-FDMA waveforms, and/orresource block interleaved FDMA waveforms from the fourth UE 115-a-4using the bidirectional link 250. The bidirectional link 250 may beassociated with the frequency F3 in the unlicensed radio frequencyspectrum band. The standalone mode may be used in non-traditionalwireless access scenarios, such as in-stadium access (e.g., unicast,multicast). An example of a type of service provider for this mode ofoperation may be a stadium owner, cable company, event host, hotel,enterprise, or large corporation that does not have access to a licensedradio frequency spectrum band. In a standalone mode, both data andcontrol may be communicated in the unlicensed radio frequency spectrumband (e.g., via the bidirectional link 250).

In some examples, a transmitting apparatus such as one of the basestations 105 described with reference to FIGS. 1 and/or 2, and/or one ofthe UEs 115 described with reference to FIGS. 1 and/or 2, may use agating interval to gain access to a channel of an unlicensed radiofrequency spectrum band (e.g., to a physical channel of the unlicensedradio frequency spectrum band). The gating interval may define theapplication of a contention-based protocol, such as an LBT protocolbased at least in part on the LBT protocol specified in EuropeanTelecommunications Standards Institute (ETSI) (EN 301 893). When using agating interval that defines the application of an LBT protocol, thegating interval may indicate when a transmitting apparatus needs toperform a contention procedure, such as a clear channel assessment(CCA). The outcome of the CCA may indicate to the transmitting devicewhether a channel of an unlicensed radio frequency spectrum band isavailable or in use for the gating interval (also referred to as an LBTradio frame or a CCA frame). When a CCA indicates that the channel isavailable (e.g., “clear” for use) for a corresponding LBT radio frame,the transmitting apparatus may reserve and/or use the channel of theunlicensed radio frequency spectrum band during part or all of the LBTradio frame by employing a channel usage beacon signal (CUBS). When theCCA indicates that the channel is not available (e.g., that the channelis in use or reserved by another apparatus), the transmitting apparatusmay be prevented from using the channel during the LBT radio frame, butmay nonetheless check for availability of the channel during subsequentLBT radio frames.

FIG. 3 shows seven TDD configurations 305 that may be used for LTE/LTE-Acommunications in an LBT radio frame transmitted over an unlicensedradio frequency spectrum band, in accordance with various aspects of thepresent disclosure. Each of the TDD configurations 305 has one of twoDL-to-UL switch-point periodicities 310—a five ms switch-pointperiodicity or a ten ms switch-point periodicity. More particularly, theTDD configurations numbered 0, 1, 2, and 6 have a five ms switch-pointperiodicity (i.e., a half-frame switch-point periodicity, and the TDDconfigurations numbered 3, 4, and 5 have a ten ms switch-pointperiodicity. The TDD configurations having a five ms switch-pointperiodicity provide a number of downlink (DL) subframes, a number ofuplink (UL) subframes, and two special (S) subframes per radio frame.The TDD configurations having a ten ms switch-point periodicity providea number of DL subframes, a number of UL subframes, and one S subframeper radio frame.

FIG. 4 shows a block diagram 400 of a base station 105-b for use inwireless communication, in accordance with various aspects of thepresent disclosure. The base station 105-b in FIG. 4 may be, forexample, one of the base stations 105 shown in FIGS. 1 and 2. The basestation 105-b shown in FIG. 4 includes a receiver 405, a controllermodule 410, and a transmitter 415. The base station 105-b may alsoinclude a processor. Each of these components may be in communicationwith each other.

The components of the base station 105-b may, individually orcollectively, be implemented with one or more application-specificintegrated circuits (ASICs) adapted to perform some or all of theapplicable functions in hardware. Alternatively, the functions may beperformed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FieldProgrammable Gate Arrays (FPGAs), and other Semi-Custom ICs), which maybe programmed in any manner known in the art. The functions of each unitmay also be implemented, in whole or in part, with instructions embodiedin a memory, formatted to be executed by one or more general orapplication-specific processors.

The receiver 405 may receive information such as packets, user data,and/or control information or signaling associated with variousinformation channels (e.g., control channels, data channels, etc.). Thereceiver 405 may receive the information wirelessly over a wirelesscommunication link using, for example, one or more LTE componentcarriers in an unlicensed and/or licensed radio frequency spectrum band.Information may be passed on to the controller module 410, and to othercomponents of the base station 105-b.

The controller module 410 may be configured to implement a number offeatures related to the transmission and receipt of information over anunlicensed radio frequency spectrum band using, for example, LTEcomponent carriers and waveforms.

In certain examples, the controller module 410 may be configured togenerate and transmit system information blocks (SIBs) over theunlicensed radio frequency spectrum band. As used herein, SIBs may alsobe referred to as evolved SIBs (eSIBs). The SIBs may include parametersrelated to the base station, including listen-before-talk (LBT)parameters, cell identifiers, and radio frame identifiers. The SIBs maybe transmitted over the unlicensed radio frequency spectrum band atregular intervals, such as during a CCA-exempt transmission (CET)subframe. In some examples, one or more of the SIBs may span an entirebandwidth of a component carrier associated with the unlicensed radiofrequency spectrum band.

The controller module 410 may be additionally or alternativelyconfigured to perform an extended CCA (ECCA) procedure to gain access tothe unlicensed radio frequency spectrum band. The ECCA procedure mayinclude performing a CCA multiple times until reaching a thresholdnumber of CCA successes (the “ECCA threshold”) is reached, indicatingthat the ECCA is successful. In some examples, the threshold number ofCCA successes may be a function of a current radio frame and/or acurrent subframe or slot, as tracked by the base station 105-b.

In some examples, the controller module 410 may cause the base station105-b to maintain an idle state after performing a successful ECCA onthe unlicensed radio frequency spectrum band and before a channel usagebeacon signal (CUBS) boundary. Following the idle period, the controllermodule 410 may cause the base station 105-b to perform a single CCA onthe unlicensed radio frequency spectrum band immediately prior to theCUBS boundary and transmit the CUBS at the CUBS boundary when the singleCCA is successful. Additionally or alternatively, the controller module410 may cause the base station 105-b to delay a transmission over theunlicensed radio frequency spectrum band until a subframe boundary or aslot boundary of a radio frame. In this way, transmissions by the basestation 105-b may be aligned with subframes and/or slots of the radioframe.

In some examples, the controller module 410 may determine that an ECCAperformed by the base station 105-b on the unlicensed radio frequencyspectrum band is unsuccessful at a CUBS boundary and continue to performthe ECCA on the unlicensed radio frequency spectrum band following theCUBS boundary in response to the determination. Upon reaching asuccessful ECCA, the base station 105-b may transmit over the unlicensedradio frequency spectrum band.

The controller module 410 may also coordinate the transmission ofsynchronization signals and/or reference signals over the unlicensedradio frequency spectrum band. In some cases, the transmission ofsynchronization signals or the transmission of reference signals mayoccur during CET subframes. In some cases a periodicity of the referencesignals may be indicative of a system frame number (SFN) timing.

The controller module 410 may further coordinate random accessprocedures at the base station 105-b to allow wireless devices (e.g.,UEs) to establish or modify radio resource control (RRC) connections orother connections. In certain examples, the controller module 405 mayreceive and process random access messages from wireless devices (e.g.,UEs). One or more of the random access messages may be received during aCET associated with the transmitting wireless device. The random accessmessages may be received over different frequency domain interlaces ofthe unlicensed radio frequency spectrum band.

The transmitter 415 may transmit one or more signals received from othercomponents of the base station 105-b. For example, the transmitter 415may transmit packets, user data, and/or control information or signalingassociated with various downlink channels (e.g., control channels, datachannels, etc.). The transmitter 415 may transmit the informationwirelessly over a wireless communication link using, for example, one ormore LTE component carriers in an unlicensed and/or licensed radiofrequency spectrum band. The transmitted information may be receivedfrom the controller module 410, and from other components of the basestation 105-b.

FIG. 5 shows a block diagram 500 of a base station 105-c for use inwireless communication, in accordance with various aspects of thepresent disclosure. The base station 105-c may be, for example, one ofthe base stations 105 shown in FIG. 1, 2, or 4, and may be an example ofone or more aspects of the base station 105-b described with referenceto FIG. 4. The base station 105-c shown in FIG. 5 includes a receiver405, a controller module 510, and a transmitter 415. The controllermodule 510 may be an example of one or more aspects of the controllermodule 410 described with reference to FIG. 4. The base station 105-cmay also include a processor, which may implement one or more aspects ofthe receiver 405, the controller module 510, or the transmitter 415.Each of these components may be in communication with each other. Thecontroller module 510 in FIG. 5 includes a radio access module 505, asystem information block (SIB) module 550, an extended clear channelassessment (ECCA) module 515, a synchronization signal module 520, areference signal module 525, and a random access module 530.

The receiver 405 may receive information such as packets, user data,and/or control information associated with various information channels(e.g., control channels, data channels, etc.), as described above withreference to FIG. 4. Information may be passed on to the controllermodule 510, and to other components of the base station 105-c. Thecontroller module 510 may be configured to perform the operationsdescribed above with reference to the controller module 410 shown inFIG. 4. The transmitter 415 may transmit one or more signals receivedfrom other components of the base station 105-c.

The radio access module 505 may control the receiver 405 and transmitter415 to enable the transmission and receipt of packets, user data, andcontrol data or signaling over unlicensed and licensed radio frequencyspectrum bands. For example, the radio access module 505 may beconfigured to implement physical layer procedures associated withgaining access to an unlicensed radio frequency spectrum band andcommunicating over the unlicensed radio frequency spectrum band usingLTE and LTE-like waveforms, or other types of cellular communications,consistent with the procedures and functionality described above withrespect to FIGS. 1-3. In particular, the radio access module 505 maycoordinate the use of listen before talk (LBT) procedures to contend foraccess to the unlicensed radio frequency spectrum band and scheduleuplink transmissions by other wireless devices (e.g., UEs) over theunlicensed radio frequency spectrum band. In certain examples, the radioaccess module 505 may be implemented within or as a component of thereceiver 405 and/or the transmitter 415.

The SIB module 550 of the controller module 510 may, in collaborationwith the receiver 405, the transmitter 415, and the radio access module505, coordinate the transmission of SIBs 550 by the base station 105-cover the unlicensed radio frequency spectrum band to one or more UEs. Insome examples, the SIBs 550 may be broadcast at regular intervals, andeach SIB may include a number of parameters related to the base station105-c. For example, the SIB parameters may include one or more LBTparameters, one or more cell identifiers, and one or more radio frameidentifiers. In certain examples, the SIB may span an entire bandwidthof a component carrier associated with the unlicensed radio frequencyspectrum band.

In some examples, the base station 105-c may transmit a SIB during aCCA-exempt transmission (CET) subframe associated with the base station105-c. The CET subframe may be periodic (e.g., every 80 ms), and the SIBmay be transmitted at each instance of the CET. Additionally, the SIBmodule 550 may cause the base station 105-c to perform a CCA prior to anon-CET subframe that is associated with opportunistic SIBtransmissions. If CCA is successful for the non-CET subframe, the SIBmodule 550 may transmit the SIB opportunistically during the non-CETsubframe. The SIB may be updated between transmissions. For example, theSIB module 550 may dynamically modify the LBT parameter between SIBtransmissions and transmit an updated version of the SIB (i.e.,containing the modified LBT parameter) at the next CET subframe oropportunistically at the next non-CET subframe associated withopportunistic SIB transmissions.

In certain examples, the SIB may transmit different redundancy versionsof the SIB at different time intervals. For example, the SIB module 550may cause a first redundancy version of the SIB to be transmitted duringCET subframes, a second redundancy version of the SIB to be transmittedduring a first interval of non-CET subframes associated withopportunistic SIB transmissions, a third redundancy version of the SIBto be transmitted during non-CET subframes associated with opportunisticSIB transmissions, and so on.

In certain examples, the cell identifier(s) signaled by the base station105-c in the SIB may be selected from the group consisting of: aphysical cell identifier (PID), an operator or PLMN identifier, a cellglobal identifier (CGI), and/or combinations thereof.

In certain examples, the LBT parameter(s) transmitted in a SIB mayinclude an ECCA counter parameter, q, used by UEs scheduled to transmitto the base station 105-c. The scheduled UEs may use the ECCA counterparameter, q, to determine a threshold number of successful CCAsindicative of ECCA success, as explained in more detail below. Inadditional or alternative examples, the LBT parameter(s) signaled in theSIB may include a CCA energy threshold. The CCA energy threshold mayindicate a threshold amount of measured energy on the unlicensed radiofrequency spectrum band indicating that the unlicensed radio frequencyspectrum band is occupied. Additionally or alternatively, the LBTparameter(s) signaled in the SIB may include a guard period for basestation resynchronization. In some cases, the ECCA procedure at the basestation may be identical for unicast and broadcast transmissions.

In certain examples, the radio frame identifier signaled in the SIB mayinclude a system frame number (SFN) or other applicable radio frameidentifier.

The ECCA module 515 of the controller module 510 may be configured toperform an ECCA on the unlicensed radio frequency spectrum band. Asdescribed elsewhere, an ECCA procedure may involve a wireless device (inthis example, the base station 105-c) performing multiple consecutiveCCAs until reaching a threshold number (the “ECCA threshold”) ofsuccessful CCAs or until a time period elapses. If the ECCA threshold isreached before the time period elapses, the ECCA is consideredsuccessful and the wireless device obtains access to transmit over theunlicensed radio frequency spectrum band. The ECCA threshold may be afunction of an individual radio frame r, subframe s, and/or slot, andmay be distributed between 1 and a maximum threshold according to adistribution function. In certain examples, all base stations associatedwith the same operator deployment may use the same algorithm (i.e., thedistribution function) to determine their individual ECCA thresholds fora given subframe or slot (with staggered radio frame, subframe, and/orslot values to randomize the distribution of ECCA thresholds among thebase stations at any given time). For example, the base station 105-cand each of the devices synchronized with the base station 105-c may usea pseudorandom generator based on a common seed to generate its ECCAthreshold for a given subframe or slot.

Parenthetically, the ECCA counter parameter q signaled to the scheduledUEs in the SIB may indicate the maximum ECCA threshold to be used by UEswhen performing ECCA for uplink transmissions to the base station 105-c.In certain examples, all UEs scheduled to transmit to the base station105-c may use the same distribution function to determine theirindividual ECCA thresholds for a given subframe or slot (with staggeredradio frame, subframe, and/or slot values to randomize the distributionof ECCA thresholds among the scheduled UEs at any given time).

Returning to the discussion of ECCAs performed by the base station 105-cfor downlink transmissions, the ECCA module 515 may be configured tocause the base station 105-c to maintain an idle state after performinga successful ECCA on the unlicensed radio frequency spectrum band andbefore a channel usage beacon signal (CUBS) boundary. Maintaining theidle state may include refraining from transmitting a CUBS immediatelyafter performing the successful ECCA. This idle state may protect otherbase stations or wireless devices that are synchronized with the basestation 105-c (e.g., wireless devices associated with the same operatoror deployment as the base station 105-c). By refraining fromtransmitting an immediate CUBS following the successful ECCA, the basestation 105-c may allow the synchronized wireless devices to continueperforming ECCA after the successful ECCA of the base station 105-cwithout additional noise from the CUBS of the base station 105-c on theunlicensed radio frequency spectrum band.

The ECCA module 515 may cause the base station 105-c to perform anadditional single CCA on the unlicensed radio frequency spectrum bandimmediately prior to the CUBS boundary. If the single CCA is successful,the base station 105-c may then transmit the CUBS at the CUBS boundary.

In additional or alternative examples, the ECCA module 515 may determinethat an ECCA performed by the base station 105-c on the unlicensed radiofrequency spectrum band is unsuccessful up to the point of the CUBSboundary. In such examples, the ECCA module 515 may cause the basestation 105-c to continue performing the ECCA on the unlicensed radiofrequency spectrum band following the CUBS boundary in response to thedetermination. If and when the ECCA is successful following the CUBSboundary, the ECCA module 515 may transmit a CUBS transmission and otherinformation over the unlicensed radio frequency spectrum band. Incertain examples, the base station 105-c may continue to perform theECCA on the unlicensed radio frequency spectrum band concurrent to atransmission by a second wireless device that is synchronized with thebase station 105-c, such as a base station or other wireless device fromthe same deployment or operator as the base station 105-c.

In additional or alternative examples, the ECCA module 515 may causetransmissions by the base station 105-c to align with subframeboundaries or slot boundaries of radio frames. Thus, when the basestation 105-c performs a successful ECCA on the unlicensed radiofrequency spectrum band, the ECCA module 515 may cause the base station105-c to delay transmission over the unlicensed radio frequency spectrumband until at least a subframe boundary of a radio frame or a slotboundary of the radio frame. The base station 105-c may then begin thetransmission at the subframe boundary or the slot boundary. As discussedabove, in some cases the base station 105-c may be synchronized with atleast a second wireless device, such as another base station. Thesubframe boundaries and/or slot boundaries of the base station 105-c maybe substantially aligned with the subframe boundaries and/or slotboundaries, respectively, of the second wireless device.

In certain examples, the ECCA module 515 may implement identical ECCAprocedures for both unicast and broadcast transmissions.

The synchronization signal module 520 of the controller module 510 maybe configured to generate and transmit synchronization signals over theunlicensed radio frequency spectrum band. In certain examples, one ormore synchronization signal(s) may be transmitted over the unlicensedradio frequency spectrum band during a CCA-exempt transmission (CET)subframe associated with the base station. The CET subframe may beperiodic (e.g., with a periodicity of 80 ms), and the synchronizationsignal(s) may be transmitted at each instance of the CET subframe. Thesynchronization signals may include a primary synchronization signal(PSS), which may be a standard PSS or an evolved PSS (ePSS), and/or asecondary synchronization signal (SSS), which may be a standard SSS oran evolved SSS (eSSS).

In addition to the CET subframes, the synchronization signal(s) may betransmitted opportunistically over one or more non-CET subframes thatare scheduled for or otherwise associated with opportunisticsynchronization signal transmissions. The synchronization signal(s) maybe transmitted over a non-CET subframe when a CCA performed prior to thenon-CET subframe is successful.

The synchronization signal(s) may be transmitted over a number ofresource blocks within a center of the unlicensed radio frequencyspectrum band, for example, the six center resource blocks of the radiofrequency spectrum band. In certain examples, the synchronizationsignal(s) may be transmitted during the first and second symbols of asubframe or slot. The synchronization signal(s) may be transmittedduring a subset of the subframes in each radio frame (e.g., subframe 0and subframe 5 of every tenth radio frame). The synchronizationsignal(s) may include physical layer cell identity (PCI) information, aswell as symbol, slot, and radio frame boundary information for the basestation 105-c.

The reference signal module 525 of the controller module 510 maycoordinate the transmission of reference signals by the base station105-c over the unlicensed radio frequency spectrum band. The referencesignal module 525 may, for example, generate a cell-specific referencesignal and transmit the cell-specific reference signal over theunlicensed radio frequency spectrum band during a CET subframeassociated with the base station 105-c. The cell-specific referencesignal (CRS) may also be referred to as an evolved CRS (eCRS).

In certain examples, the CET subframe may be periodic (e.g., with aperiodicity of 80 ms), and the cell-specific reference signal may betransmitted at each instance of the CET subframe. The cell-specificreference signal may be generated using a sequence having the sameperiodicity as the CET subframe (e.g., 80 ms). Thus, the cell-specificreference signal may indicate a system frame number (SFN) timing of thebase station 105-c.

In addition to the CET subframes, the cell-specific reference signal maybe transmitted opportunistically over one or more non-CET subframes thatare scheduled for or otherwise associated with opportunisticcell-specific reference signal transmissions. The cell-specificreference signal may be transmitted over a non-CET subframe when a CCAperformed prior to the non-CET subframe is successful.

In certain examples, the cell-specific reference signal may betransmitted during the first, second, eight, and ninth symbols of asubframe. The cell-specific reference signal may, in some examples, betransmitted during two subframes of every radio frame (subframes 0 and 5of every tenth radio frame).

The random access module 530 of the controller module 510 may beconfigured to coordinate random access procedures to establish or modifyradio resource control (RRC) connections with UEs. In certain examples,the random access module 530 may be configured to receive a randomaccess message transmitted by a wireless device, e.g., a UE, over theunlicensed radio frequency spectrum band.

In some examples, the random access message may be received at aguaranteed random access transmission opportunity during a CET subframeof the UE. Alternatively, the random access message may be receivedduring a non-CET subframe to which the UE has gained channel access bysuccessfully performing a CCA.

The random access message may be transmitted over a random accesschannel that spans an entire bandwidth of a component carrier associatedwith the unlicensed radio frequency spectrum band. The random accessmodule 530 may provide one or more random access parameters for use bythe UE to the SIB module 550, and the SIB module 550 may broadcast therandom access parameters to the UE over the unlicensed radio frequencyspectrum band prior to the UE transmitting the random access message.The random access parameter(s) may include a parameter identifying theguaranteed random access transmission opportunity, a parameteridentifying an opportunistic random access transmission opportunity,and/or combinations thereof.

In certain examples, the random access channel may include a number offrequency domain interlaces of the unlicensed radio frequency spectrumband. The random access message may be received over one of theinterlaces selected by the UE. The UE may, in some cases, randomlyselect the frequency domain interlace for transmitting the random accessmessage.

In certain examples, the random access message may include an RRCconnection request message, an RRC reconfiguration message, and/orsimilar messages.

The components of the base station 105-c may, individually orcollectively, be implemented with one or more ASICs adapted to performsome or all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on one or more integrated circuits. In other examples, othertypes of integrated circuits may be used (e.g., Structured/PlatformASICs, FPGAs, and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

FIG. 6 shows a block diagram 600 of a UE 115-b that may be used forwireless communication, in accordance with various aspects of thepresent disclosure. The UE 115-b in FIG. 6 may be, for example, one ofthe UEs 115 shown in FIGS. 1 and 2. The UE 115-b shown in FIG. 6includes a receiver 605, a controller module 610, and a transmitter 615.The UE 115-b may also include a processor. Each of these components maybe in communication with each other.

The components of the UE 115-b may, individually or collectively, beimplemented with one or more ASICs adapted to perform some or all of theapplicable functions in hardware. Alternatively, the functions may beperformed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

The receiver 605 may receive information such as packets, user data,and/or control information associated with various information channels(e.g., control channels, data channels, etc.). The receiver 605 mayreceive the information wirelessly over a wireless communication linkusing, for example, one or more LTE component carriers in an unlicensedand/or licensed radio frequency spectrum band. Information may be passedon to the controller module 610, and to other components of the UE115-b.

The controller module 610 may be configured to implement a number offeatures related to the transmission and receipt of information over anunlicensed radio frequency spectrum band using, for example, LTEcomponent carriers and waveforms.

In certain examples, the controller module 610 may be configured toreceive SIBs from a base station over the unlicensed radio frequencyspectrum band. The SIBs may include parameters related to the basestation, including LBT parameters, cell identifiers, and radio frameidentifiers. The SIBs may be received over the unlicensed radiofrequency spectrum band at regular intervals, such as during CETsubframes of the base station. In some examples, one or more of the SIBsmay span an entire bandwidth of a component carrier associated with theunlicensed radio frequency spectrum band.

The controller module 610 may be additionally or alternativelyconfigured to perform an ECCA procedure to gain access to the unlicensedradio frequency spectrum band. The ECCA procedure may include performinga CCA multiple times until reaching a threshold number of CCA successes(the “ECCA threshold”) is reached, indicating that the ECCA issuccessful. In some examples, the threshold number of CCA successes maybe a function of a current radio frame and/or a current subframe orslot, as tracked by the UE 115-b.

In some examples, the controller module 610 may cause the UE 115-b tomaintain an idle state after performing a successful ECCA on theunlicensed radio frequency spectrum band and before a CUBS boundary.Following the idle period, the controller module 610 may cause the UE115-b to perform a single CCA on the unlicensed radio frequency spectrumband immediately prior to the CUBS boundary and transmit the CUBS at theCUBS boundary when the single CCA is successful. Additionally oralternatively, the controller module 610 may cause the UE 115-b to delaya transmission over the unlicensed radio frequency spectrum band until asubframe boundary or a slot boundary of a radio frame. In this way,transmissions by the UE 115-b may be aligned with subframes and/or slotsof the radio frame.

In some examples, the controller module 610 may be configured todetermine that an ECCA performed by the UE 115-b on the unlicensed radiofrequency spectrum band is unsuccessful at a CUBS boundary and continueto perform the ECCA on the unlicensed radio frequency spectrum bandfollowing the CUBS boundary in response to the determination. Uponreaching a successful ECCA, the UE 115-b may transmit over theunlicensed radio frequency spectrum band.

The controller module 610 may also be configured to coordinate receivingsynchronization signals and/or reference signals over the unlicensedradio frequency spectrum band. In some cases, the synchronizationsignals or reference signals may be received during CET subframes of abase station. In some cases the controller module 610 may determine asystem frame number (SFN) timing based on a periodicity of the receivedreference signals.

The controller module 610 may also be configured to, based on analignment with data transmissions and subframe boundaries or slotboundaries, detect a downlink CUBS on the unlicensed radio frequencyspectrum band during a last symbol of a subframe or slot, determine thatdownlink data will be transmitted in a next subframe or slot based onthe detected CUBS, and receive the downlink data in the next subframe orslot. In certain examples, the controller module 610 may determine a TDDratio of a radio frame based on the detected CUBS.

In certain examples, the controller module 610 may be further configuredto receive a downlink CET over an unlicensed radio frequency spectrumband, determine a timing of the downlink CET, and transmit an uplink CETaccording to the determined timing of the downlink CET.

The controller module 610 may further be configured to coordinate randomaccess procedures at the UE to establish or modify RRC connections orother connections. In certain examples, the controller module 610 maygenerate random access messages and transmit the random access messagesover the unlicensed radio frequency spectrum band. The random accessmessages may be transmitted during a CET subframe of the UE oropportunistically during non-CET subframes. In some cases, thecontroller module 610 may select one of a number of frequency domaininterlaces of the unlicensed radio frequency spectrum band, where eachfrequency domain interlace is associated with a random access channel,and transmitting the random access message over the selected frequencydomain interlace.

The controller module 610 may additionally or alternatively beconfigured to identify a set of channel parameters associated with acommunication link over an unlicensed radio frequency spectrum band,select between an OFDM transmission mode and a SC-FDMA transmission modebased on the set of channel parameters, and transmit over the unlicensedradio frequency spectrum band according to the selected transmissionmode.

The transmitter 615 may transmit one or more signals received from othercomponents of the UE 115-b. For example, the transmitter 615 maytransmit packets, user data, and/or control information or signalingassociated with various uplink channels (e.g., control channels, datachannels, etc.). The transmitter 615 may transmit the informationwirelessly over a wireless communication link using, for example, one ormore LTE component carriers in an unlicensed and/or licensed radiofrequency spectrum band. For example, the transmitter 615 may transmitdata on an uplink connection to a base station 105. The transmittedinformation may be received from the controller module 610, and fromother components of the UE 115-b.

FIG. 7 shows a block diagram 700 of a UE 115-c that may be used forwireless communication, in accordance with various aspects of thepresent disclosure. The UE 115-c in FIG. 7 may be, for example, one ofthe UEs 115 shown in FIG. 1, 2, or 6, and may be an example of one ormore aspects of the UE 115-b described with reference to FIG. 6. The UE115-c shown in FIG. 7 includes a receiver 605, a controller module 710,and a transmitter 615. The UE 115-c may also include a processor. Eachof these components may be in communication with each other. Thecontroller module 710 in FIG. 7 includes a radio access module 705, asystem information block (SIB) module 750, an ECCA module 715, asynchronization signal module 720, a reference signal module 725, adownlink CUBS (D-CUBS) module 730, an uplink CET timing module 735, arandom access module 740, and an uplink transmission mode module 745.

The components of the UE 115-c may, individually or collectively, beimplemented with one or more ASICs adapted to perform some or all of theapplicable functions in hardware. Alternatively, the functions may beperformed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

The receiver 605 may receive information such as packets, user data,and/or control information associated with various information channels(e.g., control channels, data channels, etc.), as described above.Information may be passed on to the controller module 710, and to othercomponents of the UE 115-c. The controller module 710 may be an exampleof one or more aspects of the controller module 610 described withreference to FIG. 6. The controller module 710 may be configured toperform the operations described above with reference to the controllermodule 610 shown in FIG. 6. The transmitter 615 may transmit the one ormore signals received from other components of the UE 115-c, asdescribed above.

The radio access module 705 may control the receiver 605 and transmitter615 to enable the transmission and receipt of packets, user data, andcontrol data or signaling over unlicensed and licensed radio frequencyspectrum bands. For example, the radio access module 705 may beconfigured to implement physical layer procedures associated withgaining access to an unlicensed radio frequency spectrum band andcommunicating over the unlicensed radio frequency spectrum band usingLTE and LTE-like waveforms, or other types of cellular communications,consistent with the procedures and functionality described above withrespect to FIGS. 1-3. In particular, the radio access module 705 maycoordinate the use of LBT procedures to contend for access to theunlicensed radio frequency spectrum band and schedule uplinktransmissions by other wireless devices (e.g., UEs) over the unlicensedradio frequency spectrum band. In certain examples, the radio accessmodule 705 may be implemented within or as a component of the receiver605 and/or the transmitter 615.

The SIB module 750 of the controller module 710 may, in collaborationwith the receiver 605 and the radio access module 705 receive SIBs 750from a base station 105-c over the unlicensed radio frequency spectrumband. In some examples, the SIBs 750 may be broadcast at regularintervals, and each SIB may include a number of parameters related tothe base station. For example, the SIB parameters may include one ormore LBT parameters, one or more cell identifiers, and one or more radioframe identifiers. In certain examples, the SIB may span an entirebandwidth of a component carrier associated with the unlicensed radiofrequency spectrum band.

In some examples, the SIB may be received during a CET subframeassociated with the base station. The CET subframe may be periodic(e.g., every 80 ms), and the SIB may be received at each instance of theCET. Additionally, the SIB module 750 may be received at non-CETsubframes associated with opportunistic SIB transmissions. The SIB maybe updated between transmissions, and changing parameters in the SIB mayresult in modified operations at the UE 115-c. For example, the SIBmodule 750 may adjust an LBT operation based on the at least one LBTparameter received in the SIB.

In certain examples, the SIB may contain different redundancy versionsof the SIB at different time intervals. For example, a first redundancyversion of the SIB may be received during CET subframes, a secondredundancy version of the SIB may be received during a first interval ofnon-CET subframes associated with opportunistic SIB transmissions, athird redundancy version of the SIB may be received during non-CETsubframes associated with opportunistic SIB transmissions, and so on.

In certain examples, the cell identifier(s) signaled in the SIB may beselected from the group consisting of: a physical cell identifier (PID),an operator or PLMN identifier, a cell global identifier (CGI), and/orcombinations thereof.

In certain examples, the LBT parameter(s) received in the SIB mayinclude an ECCA counter parameter, q, used by the UEs 115-c to transmitto the base station. The scheduled UE 115-c may use the ECCA counterparameter, q, to determine a threshold number of successful CCAsindicative of ECCA success (the “ECCA threshold”), as explained in moredetail below. In additional or alternative examples, the LBTparameter(s) signaled in the SIB may include a CCA energy threshold. TheCCA energy threshold may indicate a threshold amount of measured energyon the unlicensed radio frequency spectrum band indicating that theunlicensed radio frequency spectrum band is occupied. Additionally oralternatively, the LBT parameter(s) signaled in the SIB may include aguard period for base station resynchronization.

In certain examples, the radio frame identifier signaled in the SIB mayinclude a system frame number (SFN) or other applicable radio frameidentifier.

The ECCA module 715 of the controller module 710 may be configured toperform an ECCA on the unlicensed radio frequency spectrum band. Asdescribed elsewhere, an ECCA procedure may involve a wireless device (inthis example, the UE 115-c) performing multiple consecutive CCAs untilreaching a threshold number (the “ECCA threshold”) of successful CCAs oruntil a time period elapses. If the ECCA threshold is reached before thetime period elapses, the ECCA is considered successful and the wirelessdevice obtains access to transmit over the unlicensed radio frequencyspectrum band. The ECCA threshold may be a function of an individualradio frame r, subframe s, and/or slot, and may be distributed between 1and a maximum threshold according to a distribution function. In certainexamples, all wireless devices synchronized with the UE 115-c (e.g., allUEs associated with the same operator or deployment) may use the samealgorithm (i.e., the distribution function) to determine theirindividual ECCA thresholds for a given subframe or slot (with staggeredradio frame, subframe, and/or slot values to randomize the distributionof ECCA thresholds among the UEs at any given time). For example, the UE115-c and each of the wireless devices synchronized with the UE 115-cmay use a pseudorandom generator based on a common seed to generate itsECCA threshold for a given subframe or slot.

The ECCA module 715 may be further configured to cause the UE 115-c tomaintain an idle state after performing a successful ECCA on theunlicensed radio frequency spectrum band and before a CUBS boundary.Maintaining the idle state may include refraining from transmitting aCUBS immediately after performing the successful ECCA. This idle statemay protect other UEs or wireless devices that are synchronized with theUE 115-c. By refraining from transmitting an immediate CUBS followingthe successful ECCA, the UE 115-c may allow the synchronized wirelessdevices to continue performing ECCA after the successful ECCA of the UE115-c without additional noise from the CUBS of the UE 115-c on theunlicensed radio frequency spectrum band. The ECCA module 715 may causethe UE 115-c to perform an additional single CCA on the unlicensed radiofrequency spectrum band immediately prior to the CUBS boundary. If thesingle CCA is successful, the UE 115-c may then transmit the CUBS at theCUBS boundary.

In additional or alternative examples, the ECCA module 715 may determinethat an ECCA performed by the UE 115-c on the unlicensed radio frequencyspectrum band is unsuccessful up to the point of the CUBS boundary. Insuch examples, the ECCA module 715 may cause the UE 115-c to continueperforming the ECCA on the unlicensed radio frequency spectrum bandfollowing the CUBS boundary in response to the determination. If andwhen the ECCA is successful following the CUBS boundary, the ECCA module715 may transmit a CUBS transmission and other information over theunlicensed radio frequency spectrum band. In certain examples, the UE115-c may continue to perform the ECCA on the unlicensed radio frequencyspectrum band concurrent to a transmission by a second wireless devicethat is synchronized with the UE 115-c, such as a base station or otherwireless device from the same deployment or operator as the UE 115-c.

In additional or alternative examples, the ECCA module 715 may causetransmissions by the UE 115-c to align with subframe boundaries or slotboundaries of radio frames. Thus, when the UE 115-c performs asuccessful ECCA on the unlicensed radio frequency spectrum band, theECCA module 715 may cause the UE 115-c to delay transmission over theunlicensed radio frequency spectrum band until at least a subframeboundary of a radio frame or a slot boundary of the radio frame. The UE115-c may then begin the transmission at the subframe boundary or theslot boundary. As discussed above, in some cases the UE 115-c may besynchronized with at least a second wireless device, such as another UE.The subframe boundaries and/or slot boundaries of the UE 115-c may besubstantially aligned with the subframe boundaries and/or slotboundaries, respectively, of the second wireless device.

The synchronization signal module 720 of the controller module 710 maybe configured to receive synchronization signals over the unlicensedradio frequency spectrum band. In certain examples, one or moresynchronization signal(s) may be received over the unlicensed radiofrequency spectrum band during a CET subframe associated with a basestation. The CET subframe may be periodic (e.g., with a periodicity of80 ms), and the synchronization signal(s) may be received at eachinstance of the CET subframe. The synchronization signals may include aprimary synchronization signal (PSS), which may be a standard PSS or anevolved PSS (ePSS), and/or a secondary synchronization signal (SSS),which may be a standard SSS or an evolved SSS (eSSS).

In addition to the CET subframes, the synchronization signal(s) may bereceived over one or more non-CET subframes that are scheduled for orotherwise associated with opportunistic synchronization signaltransmissions. The synchronization signal(s) may be received over anon-CET subframe when a CCA performed by the base station prior to thenon-CET subframe is successful.

The synchronization signal(s) may be received over a number of resourceblocks within a center of the unlicensed radio frequency spectrum band,for example, the six center resource blocks of the radio frequencyspectrum band. In certain examples, the synchronization signal(s) may bereceived during the first and second symbols of a subframe or slot. Thesynchronization signal(s) may be received during a subset of thesubframes in each radio frame (e.g., subframe 0 and subframe 5 of everytenth radio frame). The synchronization signal(s) may include PCIinformation, as well as symbol, slot, and radio frame boundaryinformation for the base station.

The reference signal module 725 of the controller module 710 may beconfigured to coordinate receiving reference signals from a base stationover the unlicensed radio frequency spectrum band. The reference signalmodule 725 may, for example, receive a cell-specific reference signalover the unlicensed radio frequency spectrum band during a CET subframeassociated with the base station. The cell-specific reference signal(CRS) may also be referred to as an evolved CRS (eCRS).

In certain examples, the CET subframe may be periodic (e.g., with aperiodicity of 80 ms), and the cell-specific reference signal may bereceived at each instance of the CET subframe. The cell-specificreference signal may be generated using a sequence having the sameperiodicity as the CET subframe (e.g., 80 ms). Thus, the referencesignal module 725 may, in some cases, be configured to determine asystem frame number (SFN) timing based on the periodicity of the cellspecific reference signal.

In addition to the CET subframes of the base station, the cell-specificreference signal may be received opportunistically over one or morenon-CET subframes of the base station that are scheduled for orotherwise associated with opportunistic cell-specific reference signaltransmissions. The cell-specific reference signal may be received over anon-CET subframe of the base station when a CCA performed by the basestation prior to the non-CET subframe is successful.

In certain examples, the cell-specific reference signal may be receivedduring the first, second, eight, and ninth symbols of a subframe. Thecell-specific reference signal may, in some examples, be received duringtwo subframes of every radio frame (subframes 0 and 5 of every tenthradio frame).

The D-CUBS module 730 of the controller module 710 may be configured todetect a CUBS from another wireless device (e.g., a base station) on theunlicensed radio frequency spectrum band during a last symbol of asubframe or slot. The D-CUBS module 730 may be further configured todetermine that downlink data will be transmitted in a next subframe orslot based on the detected CUBS, and coordinate the receiving of thedownlink data in the next subframe or slot. This determination may bebased on knowledge that transmissions in the network are aligned withsubframe and slot boundaries. In certain examples, the downlink CUBS mayspan a bandwidth of an entire component carrier of the unlicensed radiofrequency spectrum band. A sequence used for the downlink CUBS may bebased on a cell-specific reference signal sequence. In certain examples,the D-CUBS module 730 may be configured to determine a TDDdownlink-to-uplink ratio of a radio frame based on the detected CUBS.

The uplink CET timing module 735 of the controller module 710 may beconfigured to coordinate receiving a downlink CET transmission over theunlicensed radio frequency spectrum band. The uplink CET timing module735 may determine an observed timing of the downlink CET, and based on athe timing of the downlink CET, determine a timing for an uplink CET tobe transmitted by the UE 115-c. The uplink CET timing module 735 maythen cause the UE 115-c to transmit the uplink CET over the unlicensedradio frequency spectrum band according to the determined observedtiming of the downlink CET and imputed timing of the uplink CET. Incertain examples, the uplink CET timing module may determine the timingof the uplink CET based on a known or fixed offset between the downlinkCET and the uplink CET. The uplink CET may include a scheduling request(SR), a sounding reference signal (SRS), a physical uplink controlchannel (PUCCH or enhanced PUCCH (ePUCCH)), a physical random accesschannel (PRACH or enhanced PRACH (ePRACH)), and/or other signals orchannels.

The random access module 740 of the controller module 710 may beconfigured to coordinate random access procedures to establish or modifyRRC connections with a network. In certain examples, the random accessmodule 740 may be configured to generate a random access message andtransmit the random access message over the unlicensed radio frequencyspectrum band.

In some examples, the random access message may be transmitted at aguaranteed random access transmission opportunity during a CET subframeof the UE 115-c. Alternatively, the random access message may betransmitted during a non-CET subframe of the UE 115-c for which the UE115-c has gained channel access by successfully performing a CCA.

The random access message may be transmitted over a random accesschannel that spans an entire bandwidth of a component carrier associatedwith the unlicensed radio frequency spectrum band. The random accessmodule 740 may receive one or more random access parameters from a SIBbroadcast by a base station over the unlicensed radio frequency spectrumband prior to the UE 115-c transmitting the random access message. Therandom access parameter(s) may include a parameter identifying theguaranteed random access transmission opportunity, a parameteridentifying an opportunistic random access transmission opportunity,and/or combinations thereof.

In certain examples, the random access channel may include a number offrequency domain interlaces of the unlicensed radio frequency spectrumband. The UE 115-c may select one of the interlaces to transmit therandom access message. The UE 115-c may, in some cases, select thefrequency domain interlace randomly. In certain examples, the randomaccess message may include an RRC connection request message, an RRCreconfiguration message, and/or similar messages.

The uplink transmission mode module 745 of the controller module 710 maybe configured to identify a set of channel parameters associated with acommunication link over the unlicensed radio frequency spectrum band.Based on the channel parameters, the uplink transmission mode module 745may select an uplink transmission mode for the UE 115-c. Thetransmission mode may be selected from an OFDM transmission mode and aSC-FDMA transmission mode.

For example, the set of channel parameters may include a MIMO parameterindicating whether the communication link is configured for MIMOtransmissions. When MIMO is in use, the uplink transmission mode module745 may select the OFDM transmission mode for the UE 115-c. Similarly,the channel parameters may include a modulation parameter indicatingthat a modulation and coding scheme of the communication link is greaterthan a threshold. For modulation and coding schemes that are greaterthan the threshold, the uplink transmission mode module 745 may selectthe OFDM transmission mode for the UE 115-c. For lower-order modulationand coding schemes, or for scenarios where MIMO is not in use, theuplink transmission mode module 745 may select the SC-FDMA transmissionmode for uplink transmission by the UE 115-c. In certain examples, theuplink transmission mode of the communication may be selected to match adownlink transmission mode of the communication link.

FIG. 8 shows a timing diagram 800 illustrating the transmission of aplurality of parameters during a CET subframe 805 over an unlicensedradio frequency spectrum band, in accordance with various aspects of thepresent disclosure. The parameters may relate to a base station, a UE,transmissions between the base station and UE, and so forth, and mayinclude one or more of an evolved system information block (eSIB) (whichmay also be referred to simply as a system information block or SIB),evolved primary and secondary synchronization signals (ePSS, eSSS)(which may be generated at the base station), evolved common orcell-specific reference signal (eCRS), and so forth. In some examples,the eSIB may provide system information for cell discovery, and mayinclude a LBT parameter (such as an ECCA counter parameter, a CCA energythreshold, a guard period for base station resynchronization, or somecombination thereof), a cell identifier (such as a physical cellidentifier (PID), an operator (e.g., a PLMN operator) identifier, a cellglobal identifier (CGI), or some combination thereof), a radio frameidentifier (such as a system frame number (SFN)) and timing, and soforth. Thus, in some examples, a single CET subframe may be used to sendboth access parameters (for a standalone implementation) and LBT/CCAparameters (for a carrier aggregation implementation).

As mentioned, the LBT/CCA parameters may include an ECCA counterparameter, which defines a number of successful CCAs before atransmitting apparatus can initiate a CUBS and begin transmitting overthe unlicensed radio frequency spectrum band channel. A global maximum,q, for the ECCA counter parameter may be defined and advertised in theeSIB. A frame/subframe specific ECCA counter, N, may be used in specificframes/subframes, with N ranging from 1 up to the global maximum q. Asused herein, the “frame/subframe specific ECCA counter” refers to the“ECCA threshold” described with respect to previous Figures (FIGS. 4-7).The frame/subframe specific ECCA counter N may be a function of theframe (e.g., based on the radio frame identifier) and/or the subframe(e.g., the subframe identifier). The frame/subframe specific ECCAcounter N may vary in time, and may be randomly distributed between 1and q in some examples. The frame/subframe specific ECCA counter N maybe computed by base stations (e.g., eNBs), and all base stations from asingle PLMN may have identical but time-varying frame/subframe specificECCA counters N. The common counter N may be derived using a sharedalgorithm, which may be a pseudorandom generator based on a seed sharedby the base stations.

The LBT/CCA parameters may also include a CCA energy threshold, whichdefines a threshold at which a CCA will be deemed to be successful, andwhich may also be advertised in the eSIB. The LBT/CCA parameters mayalso include a guard period, which may define a period for base stationresynchronization, and which may also be advertised in the eSIB.

As illustrated in FIG. 8, the CET subframe 805 may be associated withthe unlicensed radio frequency spectrum band, and may be transmitted bya base station and received by any UEs within range of the base stationat a certain interval, such as every 80 ms. The CET subframe 805 may berelatively short—for example 1 ms as illustrated in FIG. 8. In oneexample, as shown in FIG. 8, the CET transmission subframe, includingfor example the eSIB, may be transmitted at the beginning (e.g., insubframe 0) of the 80 ms interval. The transmission of the CET subframe805 is thus periodic, and, in some examples, one or more of theparameters, such as the eSIB, may be transmitted by the base station atevery instance of the CET.

As mentioned above, in some examples, some of the parameters that aretransmitted during the CET subframe 805 may also be transmittedopportunistically at certain times in between CET subframes 805. Forexample, the eSIB may be transmitted in non-CET subframes in someexamples after the base station performs a CCA prior to the non-CETsubframe if the CCA is successful. Such non-CET transmissions of theeSIB may be at predefined intervals, such as at 20, 40, and 60 msmarkers of the 80 ms interval illustrated in FIG. 8. Non-CETtransmissions of the eSIB may be used to communicate dynamicallymodified LBT parameters and/or to provide different redundancy versionsof the eSIB at different time intervals.

Still referring to FIG. 8, in one example, the transmission of one ormore of the parameters (such as the eSIB) during the CET subframe 805may span an entire bandwidth of a component carrier associated with theunlicensed radio frequency spectrum band. For example, the eSIB may betransmitted using an entire 20 MHz component carrier for 2.4 GHz or 5GHz bands, an entire 10 MHz component carrier for a 3.5 GHz band, anentire 5 MHz component carrier for a 900 MHz band, and so forth.

FIG. 9 shows a diagram 900 of a radio frame 905 defining a plurality ofsubframes for a particular TDD configuration, in accordance with variousaspects of the present disclosure. In FIG. 9, the radio frame 905includes 10 subframes, with subframes 0, 1, 2, 3, 4, and 5 beingdownlink subframes, subframe 6 being a special subframe (which includesa shortened downlink subframe 910, an ECCA period 915, and a U-CUBSperiod 920, subframes 7 and 8 being uplink subframes, and subframe 9being another special subframe (which includes a shortened uplinksubframe 925, an ECCA period 930, and a D-CUBS period 935).

Turning to the diagram 1000 shown in FIG. 10, the ECCA subframe 1030will now be described in more detail. While FIG. 10 describes the ECCA1005 procedure for downlink transmissions, the ECCA 1005 procedure foruplink transmissions may be similar in some examples. The ECCA subframe1030 may include a plurality of CCA occasions 1040, 1045 each of whichmay be 20 microseconds (μs) long. Each CCA occasion 1040, 1045 may bedeemed successful if the energy detected is less than a CCA energy, suchas 80 dBm (which, as described above, may be advertised in the eSIB).The overall ECCA 1005 may be deemed successful if the number ofsuccessful CCA occasions 1040 is greater than the frame/subframespecific ECCA counter (with the successful CCA occasions not necessarilyneeding to be contiguous). More specifically, in one example, theframe/subframe specific counter N may be initialized at the beginning ofthe ECCA period and may be decremented by 1 with each CCA success, withthe overall ECCA 1005 being deemed successful with the counter N reaches0. In some examples, the ECCA 1005 procedure at the base station may beidentical for unicast and broadcast transmissions.

As illustrated in FIG. 10, the D-CUBS boundary 1050 may be synchronizedbased on a shared value (e.g., N) among base stations (e.g., eNBs), and,if the base station ECCA counter N is zero at the ECCA boundary 1055, anew N may be generated. In general, control and/or data transmission maybe aligned to subframe boundaries (or boundaries of slots within asubframe) based on the synchronization of one or more base stations,UEs, etc. For example, a transmission over the unlicensed radiofrequency spectrum band may be delayed, even after a successful ECCA,until at least one of a subframe boundary of a radio frame or a slotboundary of the radio frame. The base station operation during the ECCA1005 procedure may, however, not be visible to the UE; the UE may onlybe able to assume the presence of D-CUBS 1035 in the last symbol slot ofthe subframe.

FIG. 10 illustrates three different ECCA 1005 procedures, which maycorrespond to three different base stations, three different UEs, oreven to the same base station/UE pair over three different periods oftime or three different channels. Checkmarks for each CCA occasionrepresent successful CCAs occasions 1040, while an X indicates anunsuccessful CCA occasion 1045. In the first (top) ECCA 1005 illustratedin FIG. 10, the last CCA before the D-CUBS boundary 1050 is the finalcount required to deem the overall ECCA successful. In this instance,because the ECCA 1005 is successful, the transmitter (e.g., the basestation) may begin to transmit a CUBS at the CUBS boundary 1050.

In the second (middle) ECCA 1005 illustrated in FIG. 10, the ECCA 1005may clear (i.e., the number of successful CCA occasions 1040 may be met)before the D-CUBS boundary 1050. In this instance, the transmitter may,however, enter an idle state until the synchronized D-CUBS boundary 1050or just before the D-CUBS boundary 1050, thereby refraining fromtransmitting the D-CUBS immediately after the successful ECCA. In oneexample, immediately prior to the D-CUBS boundary 1050, one additionalCCA occasion may be initialized in the last CCA slot of the ECCAsubframe. If this additional CCA is successful, then the transmitter mayproceed to transmit the D-CUBS at the D-CUBS boundary 1050. In otherexamples, however, the last CCA occasion may not be used and, after theidling period, the transmitter may transmit the D-CUBS based on thesuccessful ECCA process.

In the third (bottom) ECCA 1005 illustrated in FIG. 10, the ECCA 1005may not clear (i.e., may not be deemed successful) by the D-CUBSboundary 1050. Nonetheless, CCA occasions may continue to proceedfollowing the D-CUBS boundary 1050 in order to allow the potentialtransmitter to continue to try to obtain access to the channel. In thisinstance, no D-CUBS is transmitted in the D-CUBS subframe 1035, but theECCA 1005 process may nonetheless continue in case, for example, aseparate transmitter relinquishes the channel. If the ECCA 1005 processis deemed successful sometime after the D-CUBS boundary 1050, thetransmitter may, at that time, transmit the D-CUBS and begin using thechannel for transmission.

FIG. 11 shows a diagram 1100 with more detail regarding certainsubframes of the radio frame 1105, in accordance with various aspects ofthe present disclosure. The radio frame 1105 may be an example ofaspects of the radio frame 905 described above with reference to FIG. 9.More specifically, FIG. 11 shows the location in frequency and time ofone or more synchronization signals (e.g., ePSS, eSSS, or a combinationthereof) and an eCRS signal. As mentioned above with reference to FIG.8, the ePSS, eSSS, and eCRS signals may be transmitted in subframe 0 inthe D-CET frame every 80 ms. In addition, these signals may beopportunistically provided during non-CET subframes based on ECCAsuccess—i.e., they may be provided in non-CET subframes in which thetransmitter is successful at obtaining the channel as described abovewith reference to FIG. 10.

As illustrated in FIG. 11, in one example, the ePSS, eSSS, and eCRS mayopportunistically be provided in subframes 0 and 5 (mod 10). Eachsubframe may include 14 OFDM symbols 1110. More particularly, FIG. 11shows ePSS being provided in the 6 center resource blocks (RBs) insymbol 0 of subframe 0 and/or 5 (mod 10) and eSSS being provided in the6 center RBs in symbol 1 of subframe 0 and/or 5 (mod 10), with the ePSSand eSSS providing PCI together with symbol, slot, and/or radio frameboundary information in some examples. FIG. 11 also shows an eCRS beingprovided in symbols 0, 1, 7, and 8 of subframe 0 and/or 5 (mod 10)together with enhanced physical downlink control channel (ePDCCH),enhanced physical downlink shared channel (ePDSCH), and enhancedphysical multicast channel (ePMCH), with these components spanning theentire component carrier in those symbols 1110, and the eCRS providingPCI information in some examples. In some examples, the eCRS mayimplicitly indicate a system frame number (SFN) timing such that a UEcan determine a SFN timing based on a periodicity of the sequence of theeCRS. The sequence of the eCRS may have a periodicity of 80 ms in someexamples (e.g., in standalone mode), and may be punctured in subframes1-4, 6-9 in a radio frame. In the other OFDM symbols 1110 (i.e. symbols2-6 and 9-13) of the subframes, ePDCCH, ePDSCH, and ePMCH informationmay be provided over the component carrier.

FIG. 12 shows a diagram 1200 with more detail regarding the transmissionof a D-CUB S during the radio frame described above with reference toFIG. 9, in accordance with various aspects of the present disclosure. Asillustrated in FIG. 12, the D-CUBS 1235 may be provided over the entirebandwidth of the component carrier. From the base station (e.g., eNB)perspective, the D-CUBS 1235 may be provided at variable locations intime, for example, as soon as ECCA succeeds. From the UE perspective,the D-CUBS may always be provided in symbol 13 (i.e. a last symbol 1210)of a candidate subframe. The sequence of the D-CUBS may be based on thecell-specific eCRS sequence, and the D-CUBS may include informationregarding the DL:UL ratio in a radio frame, which may change.Alternatively, this information may be provided in the same symbol 1210as the D-CUBS if not included within the D-CUBS. Also note that in someexamples, UE implementations may use D-CUBS for channel stateinformation (CSI), measurements, and so forth.

Still referring to FIG. 12, in some examples, a UE may interpret thepresence of a CUBS during the last symbol 1210 of a subframe or slot asindicating that downlink data will be transmitted in the next (i.e.,subsequent) subframe or slot based on the detected CUBS. Accordingly,the UE may prepare to and receive the downlink data in the next subframeor slot after detecting the CUBS in the last symbol 1210. The UE mayalso or alternatively determine a downlink (DL) to uplink (UL) ratio ofa TDD radio frame based on the detected CUBS—for example, the DL to UPratio may be determined based on the location of the subframe or slotwithin the radio frame in some examples.

FIG. 13 shows a diagram 1300 illustrating another timing diagram ofcertain subframes of a radio frame 1305, in accordance with variousaspects of the present disclosure. As illustrated in FIG. 13, the ePDCCH1320, ePDSCH, and ePMCH may span the entire 1 ms subframe (with theeCRS, ePSS, and eSSS not being shown in FIG. 13 for simplicity). In someexamples, UE-specific reference signal (UERS) based demodulation may beused for ePDCCH 1320, ePDSCH, and ePMCH. The UERS pattern may be builton a TM10 pattern for ePDCCH and ePDSCH, with additional tonesoptionally used for Nt estimation.

While FIGS. 8-13 have generally described processes for the downlinkportion of wireless communication, it will be appreciated than manyconcepts described are also applicable to the corresponding uplinkportions of wireless communication. For example, and the CET and ECCAprocedures described with reference to FIGS. 8 and 9 are also applicableto uplink transmissions. Turning now to FIG. 14, a diagram 1400illustrating an uplink CET (U-CET) 1410 subframe is illustrated. TheU-CET 1410 may include, for example, a scheduling request (eSR), asounding reference signal (eSRS), and so forth, and may be transmittedon a physical uplink control channel (ePUCCH), a physical random accesschannel (ePRACH), and so forth. In some examples, the U-CET timing maybe based on timing of a received downlink CET (D-CET) 1405. For example,a UE may receive a D-CET 1405, may determine the timing of the D-CET1405, and may then transmit a U-CET 1410 based on the determined timingof the D-CET 1405. The timing of the U-CET 1410 may be based on thedetermined timing of the D-CET 1405 in some examples (e.g., the timingof the U-CET 1410 may be based on a fixed offset between the D-CET 1405and U-CET 1410), and/or the D-CET 1405 may provide information regardingwhen the U-CET 1410 should be transmitted and the format the U-CET 1410should follow.

Still referring to FIG. 14, in some examples, no CCA may be required bythe transmitter, and the U-CET 1410 may include only control and othersignaling, without any data. As illustrated in FIG. 14, in someexamples, the U-CET 1410 may span the entire bandwidth of the relevantcomponent carrier, similar to the D-CET 1405, as described above.

FIG. 15 shows a diagram 1500 of one enlarged interlace of the U-CET 1410from FIG. 14. As illustrated in FIG. 15, symbol (1505) 0 of theinterface may be a resource element (RE) for eSRS and/or eSR, symbols(1505) 3 and 10 may be demodulation reference signal (DM-RS) REs forePRACH and/or ePUCCH, with the remaining symbols 1505 being data REs forePRACH, ePUCCH. FIG. 15 also illustrates that the U-CET may have a 1 msduration.

In some examples, and still referring to FIG. 15, a random accessmessage (e.g., a RRC connection request, an RRC reconfiguration message,etc.) may be generated by a wireless device (e.g., a UE), andtransmitted over an unlicensed radio frequency spectrum band at aguaranteed random access transmission opportunity during an U-CET 1410.In some instances, such a random access message may only be allowed in astandalone mode (e.g., not in a carrier aggregation mode), in order toprovide a mechanism for cell access for the UEs. The random accessmessage may be transmitted over a random access channel (e.g., ePRACH),which may span an entire bandwidth of a component carrier associatedwith the unlicensed radio frequency spectrum band. In some examples, therandom access message may be transmitted based on one or more receivedaccess parameters for transmitting the random access message. Forexample, the parameters may be received in an eSIB (described above withreference to FIG. 8), with the parameter including one or more of aparameter identifying the guaranteed random access transmissionopportunity, a parameter identifying an opportunistic random accesstransmission opportunity, and so forth. The guaranteed random accesstransmission opportunity may be available in radio frame 0 (mod 8), andthe opportunistic random access transmission may be available in otherframes or subframes based on availability of the channel as determinedby an ECCA procedure described above.

FIG. 16 shows a diagram 1600 corresponding to random access channels.The random access channels may have a multi-cluster, SC-FDMA structure,with resource block (RB) levels interleaved and being uniformly spacedin frequency. Each ePRACH may span one interlace 1605 or 10 RBs 1610. Insome examples, a UE may select one of a plurality of the frequencydomain interlaces of the unlicensed radio frequency spectrum band, witheach of the frequency domain interlaces being associated with a randomaccess channel (e.g., ePRACH). The selection of the interlace 1605 maybe done randomly and/or based on a received access parameter (e.g., theeSIB may advertise available ePRACH interlaces). The UE may alsotransmit a random access message over the selected interlace 1605, andmay in some examples do so during a U-CET subframe, or during a non-CETframe following a successful ECCA procedure. The random access messagemay be, for example, an RRC connection request, an RRC reconfigurationrequest, and so forth.

Turning now to the diagram 1700 illustrated in FIG. 17, and withreference back to the radio frame 905 illustrated in FIG. 9 and the ECCAsubframe 1030 illustrated in FIG. 10, the ECCA procedure for uplinktransmissions will now be described. As mentioned above, the ECCAprocedure for uplink transmissions is generally similar to the ECCAprocedure for downlink transmissions. For example, there may be aframe/subframe specific ECCA counter N, which may or may not be the sameas the counter in downlink ECCA, and may be advertised in the eSIBdescribed above. The uplink ECCA procedure may also include energythresholds, guard periods, and so forth, as described above withreference to FIG. 10. In FIG. 17, however, the transmission of U-CUBS1735 may be different than the transmission of D-CUBS 1035 (of FIG. 10)in some examples. For example, and as illustrated in FIG. 17, U-CUBS1735 may only be transmitted in scheduled interlaces 1710 for ePUSCH orePUCCH in some examples, with no transmissions in other, unscheduledinterlaces 1715. Furthermore, in some instances only scheduled UEs maybe allowed to transmit the U-CUBS 1735, while non-scheduled UEs continueto perform pending ECCA from previous radio frames.

FIG. 18 shows a diagram 1800 of one enlarged interlace 1805 for use inan uplink SC-FDMA transmission. As illustrated in FIG. 18, DM-RS REs forePUSCH and/or ePUCCH are transmitted over all 12 resource elements ofthe interlace 1805 during symbols (1810) 3 and 10, while data REs forePUSCH and/or ePUCCH are transmitted during the other symbols 1810. FIG.19 shows a diagram 1900 of one enlarged interlace 1905 for use in anuplink OFDMA transmission. As illustrated in FIG. 19, DM-RS REs forePUSCH are transmitted over only a subset of the 12 resource elementsduring symbols (1910) 5-6 and 12-13, while data REs are transmitted overthe remainder of the resource elements during those symbols 1910 andalso during the other symbols 1910.

Referring to both FIGS. 18 and 19, in some examples OFDMA may be usedfor uplink transmissions because of higher modulation and coding scheme(MCS) and MIMO—UE capability. In these examples, the downlink and uplinkwaveforms may be symmetrical (i.e., the uplink transmission mode of thecommunication link may match the downlink transmission mode of thecommunication link). In order to determine whether OFDMA or SC-FDMAshould be used for uplink transmissions, a set of channel parametersassociated with a communication link over an unlicensed radio frequencyspectrum band may be identified and, based on the set of parameters, atransmitter may select between OFDMA and SC-FDMA transmission modes. Forexample, if the parameters indicate that a communication link isconfigured for MIMO, a certain type of transmission mode (e.g., OFDMA)may be used. As another example, if the parameters indicate that amodulation and coding scheme for the communication link is greater thana threshold, a certain type of transmission mode (e.g., OFDMA) may beused.

FIG. 20 shows a flowchart 2000 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2000 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39. In certain examples, the blocks of the flowchart 2000 maybe performed by the controller module 410, 510, and/or 3910 as describedwith reference to FIGS. 4, 5, and/or 39.

At block 2005, the base station may generate a system information blockcomprising a plurality of parameters related to a base station, whereinthe parameters comprise at least one LBT parameter, at least one cellidentifier, and at least one radio frame identifier. In certainexamples, the functions of block 2005 may be performed by the SIB module550 as described above with reference to FIG. 5.

At block 2010, the base station may transmit the system informationblock over an unlicensed radio frequency spectrum band. In certainexamples, the functions of block 2010 may be performed by the SIB module550 as described above with reference to FIG. 5.

It should be noted that the method of flowchart 2000 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 21 shows a flowchart 2100 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2100 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 2100 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 2105, the UE may receive a system information block over anunlicensed radio frequency spectrum band, wherein the system informationblock comprises a plurality of parameters related to a base station,wherein the parameters comprise at least one LBT parameter, at least onecell identifier, and at least one radio frame identifier. In certainexamples, the functions of block 2105 may be performed by the SIB module750 as described above with reference to FIG. 7.

It should be noted that the method of flowchart 2100 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 22 shows a flowchart 2200 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2200 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39. In certain examples, the blocks of the flowchart 2200 maybe performed by the controller module 410, 510, and/or 3910 as describedwith reference to FIGS. 4, 5, and/or 39.

At block 2205, the base station may generate a system information blockcomprising a plurality of parameters related to a base station. Incertain examples, the functions of block 2205 may be performed by theSIB module 550 as described above with reference to FIG. 5.

At block 2210, the base station may transmit the system informationblock over an unlicensed radio frequency spectrum band during a CETsubframe associated with the base station. In certain examples, thefunctions of block 2210 may be performed by the SIB module 550 asdescribed above with reference to FIG. 5.

It should be noted that the method of flowchart 2200 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 23 shows a flowchart 2300 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2300 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 2300 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 2305, the UE may receive a system information block comprisinga plurality of parameters related to a base station, wherein the systeminformation block is received over an unlicensed radio frequencyspectrum band during a CET subframe associated with the base station. Incertain examples, the functions of block 2305 may be performed by theSIB module 750 as described above with reference to FIG. 7.

It should be noted that the method of flowchart 2300 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 24 shows a flowchart 2400 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2400 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5 and 39. In certain examples, the blocks of the flowchart 2400 maybe performed by the controller module 410, 510, and/or 3910 as describedwith reference to FIGS. 4, 5, and/or 39.

At block 2405, the base station may generate a system information blockcomprising a plurality of parameters related to a base station, whereinthe system information block spans an entire bandwidth of a componentcarrier associated with an unlicensed radio frequency spectrum band. Incertain examples, the functions of block 2405 may be performed by theSIB module 550 as described above with reference to FIG. 5.

At block 2410, the base station may transmit the system informationblock over the unlicensed radio frequency spectrum band. In certainexamples, the functions of block 2410 may be performed by the SIB module550 as described above with reference to FIG. 5.

It should be noted that the method of flowchart 2400 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 25 shows a flowchart 2500 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2500 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 2500 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 2505, the UE may receive a system information block comprisinga plurality of parameters related to a base station, wherein the systeminformation block is received over an unlicensed radio frequencyspectrum band, and wherein the transmission of the system informationblock spans an entire bandwidth of a component carrier associated withthe unlicensed radio frequency spectrum band. In certain examples, thefunctions of block 2505 may be performed by the SIB module 750 asdescribed above with reference to FIG. 7.

It should be noted that the method of flowchart 2500 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 26 shows a flowchart 2600 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2600 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39 or by a UE 115 or its components as described withreference to FIGS. 1, 2, 6, 7, and 40. In certain examples, the blocksof the flowchart 2600 may be performed by the controller 410, 510, 610,or 710 module as described with reference to FIGS. 4-7.

At block 2605, a wireless device may maintain an idle state afterperforming a successful ECCA on an unlicensed radio frequency spectrumband and before a CUBS boundary. In certain examples, the functions ofblock 2605 may be performed by the ECCA module 515 or 715 as describedabove with reference to FIGS. 5 and 7.

At block 2610, the wireless device may perform a single CCA on theunlicensed radio frequency spectrum band immediately prior to the CUBSboundary. In certain examples, the functions of block 2610 may beperformed by the ECCA module 515 or 715 as described above withreference to FIGS. 5 and 7.

At block 2615, the wireless device may transmit a CUBS at the CUBSboundary when the single CCA is successful. In certain examples, thefunctions of block 2615 may be performed by the ECCA module 515 or 715as described above with reference to FIGS. 5 and 7.

It should be noted that the method of flowchart 2600 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 27 shows a flowchart 2700 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2700 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39 or by a UE 115 or its components as described withreference to FIGS. 1, 2, 6, 7, and 40. In certain examples, the blocksof the flowchart 2700 may be performed by the controller module 410,510, 610, 710, 3910, or 4010 as described with reference to FIGS. 4-7,39, and 40.

At block 2705, the wireless device may determine that an ECCA performedby the wireless device on an unlicensed radio frequency spectrum band isunsuccessful at a CUBS boundary. In certain examples, the functions ofblock 2705 may be performed by the ECCA module 515 or 715 as describedabove with reference to FIGS. 5 and 7.

At block 2710, the wireless device may continue to perform the ECCA onthe unlicensed radio frequency spectrum band following the CUBS boundaryin response to the determination. In certain examples, the functions ofblock 2710 may be performed by the ECCA module 515 or 715 as describedabove with reference to FIGS. 5 and 7.

At block 2715, the wireless device may transmit over the unlicensedradio frequency spectrum band when the ECCA is successful. In certainexamples, the functions of block 2715 may be performed by the ECCAmodule 515 or 715 as described above with reference to FIGS. 5 and 7.

It should be noted that the method of flowchart 2700 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 28 shows a flowchart 2800 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2800 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39 or by a UE 115 or its components as described withreference to FIGS. 1, 2, 6, 7, and 40. In certain examples, the blocksof the flowchart 2800 may be performed by the controller module 410,510, 610, 710, 3910, or 4010 as described with reference to FIGS. 4-7,39, and 40.

At block 2805, the wireless device may determine an ECCA threshold basedon a radio frame identifier and a subframe identifier. In certainexamples, the functions of block 2805 may be performed by the ECCAmodule 515 or 715 as described above with reference to FIGS. 5 and 7.

At block 2810, the wireless device may perform an ECCA on an unlicensedradio frequency spectrum band, the ECCA comprising a plurality of CCAs.In certain examples, the functions of block 2810 may be performed by theECCA module 515 or 715 as described above with reference to FIGS. 5 and7. The ECCA may be successful if at least a number of the CCAs aresuccessful, and wherein the number of the CCAs is based on the ECCAthreshold. In certain examples, the functions of block 2815 may beperformed by the ECCA module 515 or 715 as described above withreference to FIGS. 5 and 7.

It should be noted that the method of flowchart 2800 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 29 shows a flowchart 2900 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 2900 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39 or by a UE 115 or its components as described withreference to FIGS. 1, 2, 6, 7, and 40. In certain examples, the blocksof the flowchart 2900 may be performed by the controller module 410,510, 610, 710, 3910, or 4010 as described with reference to FIGS. 4-7,39, and 40.

At block 2905, the wireless device may perform a successful ECCA on anunlicensed radio frequency spectrum band. In certain examples, thefunctions of block 2905 may be performed by the ECCA module 515 or 715as described above with reference to FIGS. 5 and 7.

At block 2910, the device may delay a transmission over the unlicensedradio frequency spectrum band until at least one of a subframe boundaryof a radio frame or a slot boundary of the radio frame. In certainexamples, the functions of block 2910 may be performed by the ECCAmodule 515 or 715 as described above with reference to FIGS. 5 and 7.

It should be noted that the method of flowchart 2900 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 30 shows a flowchart 3000 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3000 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39. In certain examples, the blocks of the flowchart 3000 maybe performed by the controller module 410, 510, and/or 3910 as describedwith reference to FIGS. 4, 5, and/or 39.

At block 3005, the base station may generate a synchronization signal.In certain examples, the functions of block 3005 may be performed by thesynchronization signal module 520 as described above with reference toFIG. 5.

At block 3010, the base station may transmit the synchronization signalover an unlicensed radio frequency spectrum band during a CET subframeassociated with the base station. In certain examples, the functions ofblock 3010 may be performed by the synchronization signal module 520 asdescribed above with reference to FIG. 5.

It should be noted that the method of flowchart 3000 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 31 shows a flowchart 3100 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3100 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 3100 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 3105, the UE may receive a synchronization signal over anunlicensed radio frequency spectrum band during a CET subframeassociated with a base station. In certain examples, the functions ofblock 3105 may be performed by the synchronization signal module 720 asdescribed above with reference to FIG. 7.

It should be noted that the method of flowchart 3100 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 32 shows a flowchart 3200 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3200 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39. In certain examples, the blocks of the flowchart 3200 maybe performed by the controller module 410, 510, and/or 3910 as describedwith reference to FIGS. 4, 5, and/or 39.

At block 3205, the base station may generate a cell-specific referencesignal. In certain examples, the functions of block 3205 may beperformed by the reference signal module 525 as described above withreference to FIG. 5.

At block 3210, the base station may transmit the cell-specific referencesignal over an unlicensed radio frequency spectrum band during a CETsubframe associated with the base station. In certain examples, thefunctions of block 3210 may be performed by the reference signal module525 as described above with reference to FIG. 5.

It should be noted that the method of flowchart 3200 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 33 shows a flowchart 3300 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3300 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 3300 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 3305, the UE may receive a cell-specific reference signal overan unlicensed radio frequency spectrum band during a CET subframeassociated with a base station. In certain examples, the functions ofblock 3305 may be performed by the reference signal module 725 asdescribed above with reference to FIG. 7.

It should be noted that the method of flowchart 3300 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 34 shows a flowchart 3400 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3400 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 3400 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 3405, the UE may detect a downlink CUBS on an unlicensed radiofrequency spectrum band during a last symbol of a subframe or slot. Incertain examples, the functions of block 3405 may be performed by the DCUBS module 730 as described above with reference to FIG. 7.

At block 3410, the UE may determine that downlink data will betransmitted in a next subframe or slot based on the detected CUBS. Incertain examples, the functions of block 3410 may be performed by the DCUBS module 730 as described above with reference to FIG. 7.

At block 3415, the UE may receive the downlink data in the next subframeor slot. In certain examples, the functions of block 3415 may beperformed by the D CUBS module 730 and/or the receiver 605 as describedabove with reference to FIG. 7.

It should be noted that the method of flowchart 3400 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 35 shows a flowchart 3500 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3500 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 3500 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 3505, the UE may receive a downlink CET over an unlicensedradio frequency spectrum band. In certain examples, the functions ofblock 3505 may be performed by the uplink CET timing module 735 and/orthe receiver 605 as described above with reference to FIG. 7.

At block 3510, the UE may determine a timing of the downlink CET. Incertain examples, the functions of block 3510 may be performed by theuplink CET timing module 735 as described above with reference to FIG.7.

At block 3515, the UE may transmit an uplink CET according to thedetermined timing of the downlink CET. In certain examples, thefunctions of block 3515 may be performed by the uplink CET timing module735 and/or the transmitter 615 as described above with reference to FIG.7.

It should be noted that the method of flowchart 3500 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 36 shows a flowchart 3600 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3600 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39 or by a UE 115 or its components as described withreference to FIGS. 1, 2, 6, 7, and 40. In certain examples, the blocksof the flowchart 3600 may be performed by the controller module 410,510, 610, 710, 3910, or 4010 as described with reference to FIGS. 4-7,39, and 40.

At block 3605, a wireless device may generate a random access message.In certain examples, the functions of block 3605 may be performed by therandom access module 530 or 740 as described above with reference toFIG. 5 or 7.

At block 3610, the wireless device may transmit the random accessmessage over an unlicensed radio frequency spectrum band at a guaranteedrandom access transmission opportunity during a CET. In certainexamples, the functions of block 3610 may be performed by the randomaccess module 530 or 740 as described above with reference to FIGS. 5and 7.

It should be noted that the method of flowchart 3600 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 37 shows a flowchart 3700 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3700 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1, 2,4, 5, and 39 or by a UE 115 or its components as described withreference to FIGS. 1, 2, 6, 7, and 40. In certain examples, the blocksof the flowchart 3700 may be performed by the controller module 410,510, 610, 710, 3910, or 4010 as described with reference to FIGS. 4-7,39, and 40.

At block 3705, the device may select one of a plurality of frequencydomain interlaces of an unlicensed radio frequency spectrum band,wherein each of the frequency domain interlaces is associated with arandom access channel. In certain examples, the functions of block 3705may be performed by the random access module 530 or 740 as describedabove with reference to FIG. 5 or 7.

At block 3710, the device may transmit a random access message over theselected frequency domain interlace of the unlicensed radio frequencyspectrum band. In certain examples, the functions of block 3710 may beperformed by the random access module 530 or 740 as described above withreference to FIGS. 5 and 7.

It should be noted that the method of flowchart 3700 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 38 shows a flowchart 3800 illustrating a method for wirelesscommunication in accordance with various aspects of the presentdisclosure. The functions of flowchart 3800 may be implemented by a UE115 or its components as described with reference to FIGS. 1, 2, 6, 7,and 40. In certain examples, the blocks of the flowchart 3800 may beperformed by the controller module 610, 710, and/or 4010 as describedwith reference to FIGS. 6, 7, and/or 40.

At block 3805, the device may identify a set of channel parametersassociated with a communication link over an unlicensed radio frequencyspectrum band. In certain examples, the functions of block 3805 may beperformed by the uplink transmission mode module 745 as described abovewith reference to FIG. 7.

At block 3810, the device may select between an OFDM transmission modeand an SC-FDMA transmission mode based on the set of channel parameters.In certain examples, the functions of block 3810 may be performed by theuplink transmission mode module 745 as described above with reference toFIG. 7.

At block 3815, the device may transmit over the unlicensed radiofrequency spectrum band according to the selected transmission mode. Incertain examples, the functions of block 3815 may be performed by theuplink transmission mode module 745 as described above with reference toFIG. 7.

It should be noted that the method of flowchart 3800 is just oneimplementation and that the operations of the method, and the steps maybe rearranged or otherwise modified such that other implementations arepossible.

FIG. 39 shows a diagram of a system 3900 for use in wirelesscommunications in accordance with various aspects of the presentdisclosure. System 3900 includes base stations 105-d, 3905-a-1,3905-a-2, which may be examples of the base stations 105 describedabove. System 3900 also includes a UE 115-d, which may be an example ofthe UEs 115 described above.

The base station 105-d may include antenna(s) 3945, a transceiver module3950, memory 3980, and a processor module 3970, which each may be incommunication, directly or indirectly, with each other (e.g., over oneor more buses). The transceiver module 3950 may be configured tocommunicate bi-directionally, via the antenna(s) 3945, with the UE 115-das well as other UEs (not shown in FIG. 39). The transceiver module 3950(and/or other components of the base station 105-d) may also beconfigured to communicate bi-directionally with one or more networks. Insome cases, the base station 105-d may communicate with the core network130-a and/or controller 3920 through network communications module 3975.Base station 105-d may be an example of an eNodeB base station, a HomeeNodeB base station, a NodeB base station, and/or a Home NodeB basestation. Controller 3920 may be integrated into base station 105-d insome cases, such as with an eNodeB base station.

Base station 105-d may also communicate with other base stations 105,such as base station 3905-a-1 and base station 3905-a-2. Each of thebase stations 105-d, 3905-a-1, 3905-a-2 may communicate with one or moreUEs using different wireless communications technologies, such asdifferent Radio Access Technologies. In some cases, base station 105-dmay communicate with other base stations such as 3905-a-1 and/or3905-a-2 utilizing base station communication module 3965. In someexamples, base station communication module 3965 may provide an X2interface within an LTE wireless communication technology to providecommunication between some of the base stations 105-d, 3905-a-1,3905-a-2. In some examples, base station 105-d may communicate withother base stations through controller 3920 and/or core network 130-b.

The memory 3980 may include random access memory (RAM) and read-onlymemory (ROM). The memory 3980 may also store computer-readable,computer-executable software (SW) code 3985 containing instructions thatare configured to, when executed, cause the processor module 3970 toperform various functions described herein (e.g., call processing,database management, message routing, etc.). Alternatively, the softwarecode 3985 may not be directly executable by the processor module 3970but may be configured to cause the computer, e.g., when compiled andexecuted, to perform functions described herein.

The processor module 3970 may include an intelligent hardware device,e.g., a central processing unit (CPU), a microcontroller, an ASIC, etc.The transceiver module 3950 may include a modem configured to modulatepackets and provide the modulated packets to the antenna(s) 3945 fortransmission, and to demodulate packets received from the antenna(s)3945. While some examples of the base station 105-d may include a singleantenna 3945, other examples of the base station 105-d include multipleantennas 3945 for multiple links which may support carrier aggregation.For example, one or more links may be used to support macrocommunications with UEs 115.

According to the architecture of FIG. 39, the base station 105-d mayfurther include a communications management module 3960. Thecommunications management module 3960 may manage communications withother base stations 105. By way of example, the communicationsmanagement module 3960 may be a component of the base station 105-d incommunication with some or all of the other components of the basestation 105-d via a bus. Alternatively, functionality of thecommunications management module 3960 may be implemented as a componentof the transceiver module 3950, as a computer program product, and/or asone or more controller elements of the processor module 3970.

The base station 105-d in FIG. 39 also includes a controller module3910, which may be an example of and/or implement some or all of thefunctionality of the controller modules 410, 510 described above withreference to FIGS. 4 and 5, including the sub-modules 505, 515, 520,525, 530, 550 described with reference to FIG. 5.

FIG. 40 shows a diagram of a system 4000 for use in wirelesscommunications in accordance with various aspects of the presentdisclosure. System 4000 includes UE 115-e which may be an example of theUEs 115 described above. System 4000 also includes a base station 105-e,which may be an example of the base stations 105 described above.

The UE 115-e shown in FIG. 40 includes antenna(s) 4040, a transceivermodule 4035, a processor module 4005, and memory 4015 (includingsoftware (SW) 4020), which each may communicate, directly or indirectly,with each other (e.g., via one or more buses 4045). The transceivermodule 4035 may be configured to communicate bi-directionally, via theantenna(s) 4040 and/or one or more wireless communication links, withone or more base stations 105-e, one or more WLAN access points, orother nodes, as described above. The transceiver module 4035 may includea modem configured to modulate packets and provide the modulated packetsto the antenna(s) 4040 for transmission, and to demodulate packetsreceived from the antenna(s) 4040. While the UE 115-e may include asingle antenna 4040 in some examples, the UE 115-e may alternativelyhave multiple antennas 4040 capable of concurrently transmitting and/orreceiving multiple wireless transmissions. The transceiver module 4035may thus be capable of concurrently communicating with one or more basestations 105-e and/or one or more other access points.

The memory 4015 may include RAM and/or ROM. The memory 4015 may storecomputer-readable, computer-executable software/firmware code 4020containing instructions that are configured to, when executed, cause theprocessor module 4005 to perform various functions described herein(e.g., make and/or execute offloading determinations). Alternatively,the software/firmware code 4020 may not be directly executable by theprocessor module 4005 but be configured to cause a computer (e.g., whencompiled and executed) to perform functions described herein. Theprocessor module 4005 may include an intelligent hardware device, e.g.,a CPU, a microcontroller, an ASIC, etc. may include RAM and ROM.

The UE 115-e also includes a controller module 4010, which may be anexample of and/or implement some or all of the functionality of thecontroller modules 610, 710 described above with reference to FIGS. 6and 7, including the sub-modules 705, 715, 720, 725, 730, 735, 740, 745,750 described with reference to FIG. 7.

The detailed description set forth above in connection with the appendeddrawings describes examples and does not represent the only examplesthat may be implemented or that are within the scope of the claims. Theterms “example” and “exemplary,” when used in this description, mean“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand apparatuses are shown in block diagram form in order to avoidobscuring the concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on anon-transitory computer-readable medium. Other examples andimplementations are within the scope and spirit of the disclosure andappended claims. For example, due to the nature of software, functionsdescribed above can be implemented using software executed by aprocessor, hardware, firmware, hardwiring, or combinations of any ofthese. Features implementing functions may also be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations. Also, as usedherein, including in the claims, “or” as used in a list of itemsprefaced by “at least one of” indicates a disjunctive list such that,for example, a list of “at least one of A, B, or C” means A or B or C orAB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, electrically erasableprogrammable ROM (EEPROM), compact disc ROM (CD-ROM) or other opticaldisk storage, magnetic disk storage or other magnetic storage devices,or any other medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1×, 1X, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMTM,etc. UTRA and E-UTRA are part of Universal Mobile TelecommunicationSystem (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A)are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE,LTE-A, and GSM are described in documents from an organization named“3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the systems and radio technologies mentioned above as well asother systems and radio technologies. The description below, however,describes an LTE system for purposes of example, and LTE terminology isused in much of the description below, although the techniques areapplicable beyond LTE applications.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. (canceled)
 2. A method of wireless communication, comprising:transmitting at least one system information block (SIB), wherein theSIB comprises a Multiple Input Multiple Output (MIMO) parameter and amodulation parameter associated with a communication link over anunlicensed radio frequency spectrum band; and receiving a transmissionover the unlicensed radio frequency spectrum band according to aselected transmission mode based at least on the MIMO parameter and themodulation parameter, wherein the selected transmission mode comprisesan orthogonal frequency division multiplexing (OFDM) transmission modewhen the MIMO parameter indicates that the communication link supportsMIMO transmissions and the selected transmission mode comprises asingle-carrier frequency division multiple access (SC-FDMA) transmissionmode when the modulation parameter for the communication link is lessthan or equal to a threshold.
 3. The method of claim 2, wherein themodulation parameter is a modulation and coding scheme (MCS) parameter.4. The method of claim 2, wherein the receiving comprises receiving anuplink transmission and the selected transmission mode comprises anuplink transmission mode of the communication link.
 5. The method ofclaim 4, wherein the uplink transmission mode of the communication linkmatches a downlink transmission mode of the communication link.
 6. Themethod of claim 2, wherein the receiving comprises receiving over aplurality of interlaced resource blocks.
 7. The method of claim 2,wherein the selected transmission mode comprises the OFDM transmissionmode, and wherein receiving comprises receiving a demodulation referencesignal for the communication link according to a subset of resourceelements of one or more symbols of one or more resource blocks.
 8. Themethod of claim 7, wherein, for the OFDM transmission mode, thereceiving comprises receiving data in resource elements of the one ormore symbols other than the subset of resource elements.
 9. The methodof claim 2, wherein the selected transmission mode comprises the SC-FDMAtransmission mode, the receiving comprises receiving a demodulationreference signal for the communication link using each resource elementof one or more symbols of one or more resource blocks.
 10. An apparatusfor wireless communication, comprising: a processor; memory inelectronic communication with the processor; and instructions stored inthe memory, wherein the instructions are executable by the processor to:transmit at least one system information block (SIB), wherein the SIBcomprises a Multiple Input Multiple Output (MIMO) parameter and amodulation parameter associated with a communication link over anunlicensed radio frequency spectrum band; and receive a transmissionover the unlicensed radio frequency spectrum band according to aselected transmission mode based at least on the MIMO parameter and themodulation parameter, wherein the selected transmission mode comprisesan orthogonal frequency division multiplexing (OFDM) transmission modewhen the MIMO parameter indicates that the communication link supportsMIMO transmissions and the selected transmission mode comprises asingle-carrier frequency division multiple access (SC-FDMA) transmissionmode when the modulation parameter for the communication link is lessthan or equal to a threshold.
 11. The apparatus of claim 10, wherein themodulation parameter is a modulation and coding scheme (MCS) parameter.12. The apparatus of claim 10, wherein receive comprises receive anuplink transmission and the selected transmission mode comprises anuplink transmission mode of the communication link.
 13. The apparatus ofclaim 12, wherein the uplink transmission mode of the communication linkmatches a downlink transmission mode of the communication link.
 14. Theapparatus of claim 10, wherein receive comprises receive over aplurality of interlaced resource blocks.
 15. The apparatus of claim 10,wherein the selected transmission mode comprises the OFDM transmissionmode, and wherein receive comprises receive a demodulation referencesignal for the communication link according to a subset of resourceelements of one or more symbols of one or more resource blocks.
 16. Theapparatus of claim 15, wherein, for the OFDM transmission mode, receivecomprises receive data in resource elements of the one or more symbolsother than the subset of resource elements.
 17. The apparatus of claim10, wherein the selected transmission mode comprises the SC-FDMAtransmission mode, and wherein receive comprises receive a demodulationreference signal for the communication link using each resource elementof one or more symbols of one or more resource blocks.
 18. Anon-transitory computer-readable medium storing code for wirelesscommunication, code comprising instructions executable to: transmit atleast one system information block (SIB), wherein the SIB comprises aMultiple Input Multiple Output (MIMO) parameter and a modulationparameter associated with a communication link over an unlicensed radiofrequency spectrum band; and receive a transmission over the unlicensedradio frequency spectrum band according to a selected transmission modebased at least on the MIMO parameter and the modulation parameter,wherein the selected transmission mode comprises an orthogonal frequencydivision multiplexing (OFDM) transmission mode when the MIMO parameterindicates that the communication link supports MIMO transmissions andthe selected transmission mode comprises a single-carrier frequencydivision multiple access (SC-FDMA) transmission mode when the modulationparameter for the communication link is less than or equal to athreshold.
 19. The non-transitory computer-readable medium of claim 18,wherein the modulation parameter is a modulation and coding scheme (MCS)parameter.
 20. The non-transitory computer-readable medium of claim 18,wherein the instructions executable to receive comprise instructionsexecutable to receive an uplink transmission and the selectedtransmission mode comprises an uplink transmission mode of thecommunication link.
 21. The non-transitory computer-readable medium ofclaim 20, wherein the uplink transmission mode of the communication linkmatches a downlink transmission mode of the communication link.
 22. Thenon-transitory computer-readable medium of claim 18, wherein theinstructions executable to receive comprise instructions executable toreceive over a plurality of interlaced resource blocks.
 23. Thenon-transitory computer-readable medium of claim 18, wherein theselected transmission mode comprises the OFDM transmission mode, andwherein the instructions executable to receive comprise instructionsexecutable to receive a demodulation reference signal for thecommunication link using a subset of resource elements of one or moresymbols of one or more resource blocks.
 24. The non-transitorycomputer-readable medium of claim 23, wherein, for the OFDM transmissionmode, the instructions executable to receive comprise instructionsexecutable to receive data in resource elements of the one or moresymbols other than the subset of resource elements.
 25. Thenon-transitory computer-readable medium of claim 18, wherein theselected transmission mode comprises the SC-FDMA transmission mode, theinstructions executable to receive comprise instructions executable toreceive a demodulation reference signal for the communication link usingeach resource element of one or more symbols of one or more resourceblocks.